Ofcom has published its long-expected consultation on additional measures that it recommends U2U platforms and search engines should implement to fulfil their duties under the Online Safety Act. The focus, this time, is almost entirely on proactive technology: automated systems intended to detect particular kinds of illegal content and content harmful to children, with a view to blocking or swiftly removing them.
The consultation marks a further step along the UK’s diverging path from the EU Digital Services Act. The DSA prohibits the imposition of general monitoring obligations on platforms. Those are just the kind of obligations envisaged by the Online Safety Act’s preventative duties, which Ofcom is gradually fleshing out and implementing.
Ofcom finalised its first Illegal Harms Code of Practice in December 2024. For U2U services the Code contained two proactive technology recommendations: hash and URL matching for CSAM. The initial consultation had also suggested fuzzy keyword matching to detect some kinds of fraud, but Ofcom did not proceed with that. The regulator indicated that it would revisit fraud detection in a later, broader consultation. That has now arrived.
The new U2U proposals go beyond fraud. They propose perceptual hash-matching for visual terrorism content and for intimate image abuse content. They suggest that content should be excluded from recommender feeds if there are indications that it is potentially illegal, unless and until it is determined via content moderation to be legal.
Most ambitiously, Ofcom wants certain relatively large platforms to research the availability and suitability (in accordance with proposed criteria) of proactive technology for detection of fraud and some other illegal behaviour, then implement it if appropriate. Those platforms would also have to review existing technologies that they use for these purposes and, if feasible, bring them into line with Ofcom’s criteria.
Ofcom calls this a ‘principles-based’ measure, probably because it describes a qualitative evaluation and configuration process rather than prescribing any concrete parameters within which the technology should operate.
Freedom of expression
Legal obligations for proactive content detection, blocking and removal engage the fundamental freedom of expression rights of users. Obligations must therefore comply with ECHR human rights law, including requirements of clarity and certainty.
Whilst a principles-based regime may be permissible, it must nevertheless be capable of predictable application. Otherwise it will stray into impermissible vagueness. Lord Sumption in Catt said that what is required is a regime the application of which is:
“reasonably predictable, if necessary with the assistance of expert advice. But except perhaps in the simplest cases, this does not mean that the law has to codify the answers to every possible issue which may arise. It is enough that it lays down principles which are capable of being predictably applied to any situation.”
In Re Gallagher he said that:
“A measure is not “in accordance with the law” if it purports to authorise an exercise of power unconstrained by law. The measure must not therefore confer a discretion so broad that its scope is in practice dependent on the will of those who apply it, rather than on the law itself. Nor should it be couched in terms so vague or so general as to produce substantially the same effect in practice.”
Typically these strictures would apply to powers and duties of public officials. The Online Safety Act is different: it requires U2U service providers to make content decisions and act (or not) to block or remove users’ posts. Thus the legal regime that requires them to do that has to provide sufficient predictability of their potential decisions and resulting acts.
In addition to fraud and financial services offences, Ofcom’s proposed principles-based measures would apply to image based CSAM, CSAM URLs, grooming, and encouraging or assisting suicide (or attempted suicide).
Any real-time automated content moderation measure poses questions about human rights compatibility. The auguries are not promising: proactive technology, armed only with the user’s post and perhaps some other on-platform data, will always lack contextual information. For many offences off-platform information can be the difference between guilt and innocence. Decisions based on insufficient information inevitably stray into arbitrariness.
Then there is the trade-off between precision and recall. Typically, the more target content the automated tool is tuned to catch, the more false positives it will also throw up. False positives result in collateral damage to legitimate speech. It does not take many false positives to constitute disproportionate interference with users’ rights of freedom of expression.
Lord Grade, the Chairman of Ofcom, said in a recent speech that the aims of tackling criminal material and content that poses serious risks of harm to children’s physical or emotional health were not in conflict with freedom of expression. Indeed so, but focusing only on the aim misses the point: however worthy the end, it is the means – in this case proactive technology – that matters.
Prescribed by law
Ofcom’s Proactive Technology Draft Guidance says this about proportionality of the proposed measures:
“Proactive technology used for detection of harmful content involves making trade-offs between false positives and false negatives. Understanding and managing those trade-offs is essential to ensure the proactive technology performs proportionately, balancing the risk of over-removal of legitimate content with failure to effectively detect harm.” (para 5.14)
Proportionality is a requirement of human rights compliance. However, before considering proportionality a threshold step has to be surmounted: the ‘prescribed by law’ or ‘legality’ condition. This is a safeguard against arbitrary restrictions – laws should be sufficiently precise and certain that they have the quality of law.
The prescribed by law requirement is an aspect of the European Convention on Human Rights. It has also been said to be a UK constitutional principle that underpins the rule of law:
“The acceptance of the rule of law as a constitutional principle requires that a citizen, before committing himself to any course of action, should be able to know in advance what are the legal consequences that will flow from it.” (Lord Diplock, Black-Clawson [1975])
The Constitutional Reform Act 2005 refers in S.1 to:
“the existing constitutional principle of the rule of law”.
For content monitoring obligations the quality of law has two facets, reflecting the potential impact of the obligations on the fundamental rights of both platforms and users.
The platform aspect is written in to the Act itself:
“the measures described in the code of practice must be sufficiently clear, and at a sufficiently detailed level, that providers understand what those measures entail in practice”. (Schedule 4)
The user aspect is not spelled out in the Act but is no less significant for that. Where a user’s freedom of speech may be affected by steps that a platform takes to comply with its duties, any interference with the user’s right of freedom of expression must be founded on a clear and precise rule.
That means that a user must be able to foresee in advance with reasonable certainty whether something that they have in mind to post is or is not liable to be blocked, removed or otherwise affected as a result of the obligations that the Act places on the platform.
That is not simply a matter of users themselves taking care to comply with substantive law when they consider posting content. The Act interpolates platforms into the process and may require them to make judgements about whether the user’s post is or is not illegal. Foreseeability is therefore a function both of the substantive law and of the rules about how a platform should make those judgements.
If, therefore, the mechanism set up by the Act and Ofcom for platforms to evaluate, block and take down illegal content is likely to result in unpredictable, arbitrary determinations of what is and is not illegal, then the mechanism fails the ‘prescribed by law’ test and is a per se violation of the right of freedom of expression.
Equally, if the regime is so unclear about how it would operate in practice that a court is not in a position to assess its proportionality, that would also fail the ‘prescribed by law’ test. That is the import of Lord Sumption’s observations in Catt and Gallagher (above).
A prescriptive bright-line rule, however disproportionate it might be, would satisfy the ‘prescribed by law’ test and fall to be assessed only by reference to necessity and proportionality. Ofcom’s principles-based recommendations, however, are at the opposite end of the spectrum: they are anything but a bright-line rule. The initial ‘prescribed by law’ test therefore comes into play.
How do Ofcom’s proposed measures stack up?
Service providers themselves would decide how accurate the technology has to be, what proportion of content detected by the technology should be subjected to human review, and what is an acceptable level of false positives.
Whilst Ofcom specifies various ‘proactive technology criteria’, those are expressed as qualitative factors to be taken into account, not quantitative parameters. Ofcom does not specify what might be an appropriate balance between precision and recall, nor what is an appropriate proportion of human review of detected content.
Nor does Ofcom indicate what level of false positives might be so high as to render the technology (alone, or in combination with associated procedures) insufficiently accurate.
Examples of Ofcom’s approach include:
“However, there are some limitations to the use of proactive technology in detecting or supporting the detection of the relevant harms. For example, proactive technology does not always deal well with nuance and context in the same way as humans.
However, we mitigate this through the proactive technology criteria which are designed to ensure proactive technology is deployed in a way that ensures an appropriate balance between precision and recall, and that an appropriate proportion of content is reviewed by humans.” (Consultation, para 9.92)
“Where a service has a higher tolerance for false positives, more content may be wrongly identified. … The extent of false positives will depend on the service in question and the way in which it configures its proactive technology. The measure allows providers flexibility in this regard, including as to the balance between precision and recall (subject to certain factors set out earlier in this chapter).” (Consultation, paras 9.135, 9.136)
“… when determining what is an appropriate proportion of detected content to review by humans, providers have flexibility to decide what proportion of detected content it is appropriate to review, however in so doing, providers should ensure that the following matters are taken into account…” (Consultation, para 9.19)
“However, in circumstances where false positives are consistently high and cannot be meaningfully reduced or mitigated, particularly where this may have a significant adverse impact on user rights, providers may conclude that the proactive technology is incapable of meeting the criteria.” (Proactive Technology Draft Guidance, para 5.19)
How high is high? How significant is significant? No answer is given, other than that the permissible level of false positives is related to the nature of the subsequent review of detected content. As we shall see, the second stage review does not require all content detected by the proactive technology to be reviewed by human beings. The review could, seemingly, be conducted by a second automated system.
The result is that two service providers in similar circumstances could arrive at completely different conclusions as to what constitutes an acceptable level of legitimate speech being blocked or taken down. Ofcom acknowledges that the flexibility of its scheme:
“could lead to significant variation in impact on users’ freedom of expression between services”. (Consultation, para 9.136)
That must raise questions about the predictability and foreseeability of the regime.
If the impact on users’ expression is not reasonably foreseeable, that is a quality of law failure and no further analysis is required. If that hurdle were surmounted, there is still the matter of what level of erroneous blocking and removal would amount to a disproportionate level of interference with users’ legitimate freedom of expression.
Proportionality?
Ofcom concludes that:
“Having taken account of the nature and severity of the harms in question, the principles we have built into the measure to ensure that the technology used is sufficiently accurate, effective and lacking in bias, and the wider range of safeguards provided by other measures, we consider overall that the measure’s potential interference to users’ freedom of expression to be proportionate.” (Consultation, para 9.154)
However, it is difficult to see how Ofcom (or anyone else) can come to any conclusion as to the overall proportionality of the recommended principles-based measures when they set no quantitative or concrete parameters for precision versus recall, accuracy of review of suspect content, or an ultimately acceptable level of false positives.
Ofcom’s discussion of human rights compliance starts with proportionality. While it notes that the interference must be ‘lawful’, there is no substantive discussion of the ‘prescribed by law’ threshold.
Prior restraint
Finally, on the matter of human rights compatibility, proactive detection and filtering obligations constitute a species of prior restraint (Yildirim v Turkey (ECtHR), Poland v The European Parliament and Council (CJEU)).
Prior restraint is not impermissible. However, it does require the most stringent scrutiny and circumscription, in which risk of removal of legal content will loom large. The ECtHR in Yildirim noted that “the dangers inherent in prior restraints are such that they call for the most careful scrutiny on the part of the Court”.
The proactive technology criteria
Ofcom’s proactive technology criteria are, in reality, framed not as a set of criteria but as a series of factors that the platform should take into account. Ofcom describes them as “a practical, outcomes-focused set of criteria.” [Consultation, para 9.13]
Precision and recall: One criterion is that the technology has been evaluated using “appropriate” performance metrics and
“configured so that its performance strikes an appropriate balance between precision and recall”. (Recommendation C11.3(c))
Ofcom evidently must have appreciated that, without elaboration, “appropriate” was an impermissibly vague determinant. The draft Code of Practice goes on (Recommendation C11.4(a)):
“when configuring the technology so that it strikes an appropriate balance between precision and recall, the provider should ensure that the following matters are taken into account:
i) the service’s risk of relevant harm(s), reflecting the risk assessment of the service and any information reasonably available to the provider about the prevalence of target illegal content on the service;
ii) the proportion of detected content that is a false positive;
iii) the effectiveness of the systems and/or processes used to identify false positives; and
iv) in connection with CSAM or grooming, the importance of minimising the reporting of false positives to the National Crime Agency (NCA) or a foreign agency;”
These factors may help a service provider tick the compliance boxes – ‘Yes, I have taken these factors into account’ – but they do not amount to a concrete determinant of what constitutes an appropriate balance between precision and recall.
Review of detected content: Accuracy of the proactive technology is, as already alluded to, only the first stage of the recommended process. The service provider has to treat a detected item as providing ‘reason to suspect’ that it is illegal content, then move on to a second stage: review.
“Where proactive technology detects or supports the detection of illegal content and/or content harmful to children, providers should treat this as reason to suspect that the content may be target illegal content and/or content harmful to children.
Providers should therefore take appropriate action in line with existing content moderation measures, namely ICU C1 and ICU C2 (in the Illegal Content User-to-user Codes of Practice) and PCU C1 and PCU C2 (in the Protection of Children User-to-user Code of Practice), as applicable.” (Consultation, para 9.74)
That is reflected in draft Codes of Practice paras ICU C11.11, 12.9 and PCU C9.9, 10.7. For example:
“ICU C11.11 Where proactive technology detects, or supports the detection of, target illegal content in accordance with ICU C11.8(a), the provider should treat this as reason to suspect that the content may be illegal content and review the content in accordance with Recommendation ICU C1.3.”
‘Review’ does not necessarily mean human review. Compliance with the proactive technology criteria requires that:
“…policies and processes are in place for human review and action is taken in accordance with that policy, including the evaluation of outputs during development (where applicable), and the human review of an appropriate proportion of the outputs of the proactive technology during deployment. Outputs should be explainable to the extent necessary to support meaningful human judgement and accountability.” (Emphasis added) (draft Code of Practice Recommendation ICU C11.3(g))
The consultation document says:
“It should be noted that this measure does not itself recommend the removal of detected content. Rather, it recommends that providers moderate detected content in accordance with existing content moderation measures (subject to human review of an appropriate proportion of detected content, as mentioned above).” (Consultation, para 9.147)
And:
“Providers have flexibility in deciding what proportion of detected content is appropriate to review, taking into account [specified factors]” (Consultation, para 9.145)
Ofcom has evidently recognised that “appropriate proportion” is, without elaboration, another impermissibly vague determinant. It adds (Recommendation C11.4(b)):
“when determining what is an appropriate proportion of detected content to review by humans, the provider should ensure that the following matters are taken into account:
i) the principle that the resource dedicated to review of detected content should be proportionate to the degree of accuracy achieved by the technology and any associated systems and processes;
ii) the principle that content with a higher likelihood of being a false positive should be prioritised for review; and
iii) in the case of CSAM or grooming, the importance of minimising the reporting of false positives to the NCA or a foreign agency.”
As with precision and recall, these factors may help a service provider tick the compliance boxes but are not a concrete determinant of the proportion of detected content to be submitted to human review in any particular case.
Second stage review – human, more technology or neither?
The upshot of all this appears to be that content detected by the proactive technology should be subject to review in accordance with the Code of Practice moderation recommendations; and that an ‘appropriate proportion’ of that content should be subject to human review.
But if only an ‘appropriate proportion’ of content detected by the proactive technology has to be subject to human review, how is the rest to be treated? Since it appears that some kind of ‘appropriate action’ is contemplated in accordance with Ofcom’s content moderation recommendations, the implication appears to be that moderation at the second stage could be by some kind of automated system.
In that event it would seem that the illegal content judgement itself would be made by that second stage technology in accordance with Recommendation C1.3.
Recommendation C1.3, however, does not stipulate the accuracy of second stage automated technology. The closest that the Code of Practice comes is ICU C4.2 and 4.3:
“The provider should set and record performance targets for its content moderation function, covering at least:
a) the time period for taking relevant content moderation action; and
b) the accuracy of decision making.
In setting its targets, the provider should balance the need to take relevant content moderation action swiftly against the importance of making accurate moderation decisions.”
Once again, the path appears to lead to an unpredictable balancing exercise by a service provider.
Curiously, elsewhere Ofcom appears to suggest that second stage “complementary tools” could in some cases merely be an ‘additional safeguard’:
“What constitutes an appropriate balance between precision and recall will depend on the nature of the relevant harm, the level of risk identified and the service context. For example, in some cases a provider might optimise for recall to maximise the quantity of content detected and apply additional safeguards, such as use of complementary tools or increased levels of human review, to address false positives. In other cases, higher precision may be more appropriate, for example, to reduce the risk of adverse impacts on user rights.” (Proactive Technology Draft Guidance, para 5.18)
If the implication of ‘in some cases’ is that in other cases acting on the output of the proactive technology without a second stage review would suffice, that would seem to be inconsistent with the requirement that all detected content be subject to some kind of moderation in accordance with Recommendation C1.3.
Moreover, under Ofcom’s scheme proactive technology is intended only to provide ‘reason to suspect’ illegality. That would not conform to the standard stipulated by the Act for an illegal content judgement: ‘reasonable grounds to infer’.
Conclusion
When, as Ofcom recognises, the impact on users’ freedom of expression will inevitably vary significantly between services, and Ofcom’s documents do not condescend to what is or is not an acceptable degree of interference with legitimate speech, it is difficult to see how a user could predict, with reasonable certainty, how their posts are liable to be affected by platforms’ use of proactive technology in compliance with Ofcom’s principles-based recommendations.
Nor is it easy to see how a court would be capable of assessing the proportionality of the measures. As Lord Sumption observed, the regime should not be couched in terms so vague or so general as, substantially, to confer a discretion so broad that its scope is in practice dependent on the will of those who apply it. Again, Ofcom’s acknowledgment that the flexibility of its scheme could lead to significant variation in impact on users’ freedom of expression does not sit easily with that requirement.
Ofcom, it should be acknowledged, is to an extent caught between a rock and a hard place. It has to avoid being overly technology-prescriptive, while simultaneously ensuring that the effects of its recommendations are reasonably foreseeable to users and capable of being assessed for proportionality. Like much else in the Act, that may in reality be an impossible circle to square. That does not bode well for the Act’s human rights compatibility.
Graham Smith, Of Counsel, Bird & Bird LLP
This article represents the personal views of the author. It first appeared on his Cyberleagle blog
