5.1. Sanctions must fully comply with the three-prong test
The three-prong test (see Assembly Section 4.4) does not only apply to restrictions placed on an assembly before or during the event, but also to restrictions – such as sanctions – imposed afterwards.
In Praded v. Belarus, for example, the author of the communication had been given an administrative fine in connection with an unauthorised protest at the Iranian embassy. The HRC held that the proportionality of that fine needed to be demonstrated:
[W]hile ensuring the security and safety of the embassy of the foreign State may be regarded as a legitimate purpose for restricting the right to peaceful assembly, the State party must justify why the apprehension of the author and imposition on him of an administrative fine were necessary and proportionate to that purpose.
The starting point is that the imposition of any sanction – however minor – amounts to a restriction of the right and thus requires a clear justification. The ECtHR has repeatedly held that even sanctions at the lower end of the scale should not be imposed on participants in an assembly that has not been forbidden unless the defendant has personally committed a “reprehensible act”:
[T]he freedom to take part in a peaceful assembly is of such importance that a person cannot be subject to a sanction – even one at the lower end of the scale of disciplinary penalties – for participation in a demonstration which has not been prohibited, so long as that person does not himself commit any reprehensible act on such an occasion.
Acts the ECtHR has considered reprehensible include throwing rocks at the police, the incitement of inter-ethnic violence and damaging property. A person does not commit a reprehensible act by failing to disavow an assembly when others resort to such acts. The ECtHR recently accepted that obstructing major highways in disregard of police orders may also be qualified as reprehensible. The UN Special Rapporteur expressed his regret at this latter decision.
If there are grounds to apply a penalty, the ECtHR will scrutinize whether the nature (criminal or administrative) and the severity of penalties of penalties is justified:
The nature and severity of the penalties imposed are also factors to be taken into account when assessing the proportionality of an interference in relation to the aim pursued. 
The Court has warned that, even if they are not imposed in practice, high fines are “conducive to creating a ‘chilling effect’ on legitimate recourse to protests.”
5.2. Criminal law should in principle not be used in response to a peaceful assembly
There is increasing concern globally about the criminalization of persons who exercise the right to assemble; a concern expressed by, among others, the UN Special Rapporteur. “Criminalization” refers to administrative or criminal measures taken to sanction participants or organizers of assemblies.
A number of international courts and mechanisms have made it clear that the application of criminal or administrative sanctions to organizers of or participants in peaceful assemblies warrants particular scrutiny; in principle there should be no threat of sanctions for participation in assemblies. This is true all the more of the imposition of prison sentences.
The ECtHR’s position is as follows:
Where the sanctions imposed on the demonstrators are criminal in nature, they require particular justification. A peaceful demonstration should not, in principle, be rendered subject to the threat of a criminal sanction, and notably to deprivation of liberty. Thus, the Court must examine with particular scrutiny the cases where sanctions imposed by the national authorities for non-violent conduct involve a prison sentence.
The ECtHR has noted that in some legal systems, administrative law is used to punish offences that are criminal in nature. Where sanctions imposed are punitive and deterrent in nature, and in particular where individuals are deprived of their liberty, even briefly, the Court classifies these measures as “criminal”, even if they are considered administrative under national law.
The IACHR has published an extensive report on the “Criminalization of the Work of Human Rights Defenders” in which it expresses its concern about the overuse of criminal law in a number of contexts, including in response to protest. In particular, it voices its
concern about the existence of provisions that make criminal offenses out of the mere participation in a protest, road blockages (at any time and of any kind), or acts of disorder that in reality, in and of themselves, do not adversely affect legally protected rights such as those to life, security, or the liberty of individuals.