By Veronique Robert, defense lawyer, criminal law
"Illegal demonstration" is not a performative utterance.
In other words, the police declaring a demonstration illegal does not mean that the demonstration is illegal, much less that participants are committing an illegal act by the mere fact of their presence.
"Illegal demonstration" is not even a legal concept.
In other words, the police declaring a demonstration illegal only means that from that moment on, they assume the right to disperse it, to clamp down on it, to break it. As we have seen a few times in these last weeks, they also assume for themselves the right to charge against demonstrators, and to detain some of them, for reasons still unknown to the public insofar as no charges have been filed, except for breach of conditions.
The Criminal Code contains two offences similar to the notion of "illegal demonstration": unlawful assembly and riot.
“Unlawful assembly” is the gathering of three or more persons who convene in such a manner as to cause fear, on reasonable grounds, within a particular environment, that they will tumultuously disturb the peace. 
“Riot” is an unlawful assembly that goes beyond causing fear it will disturb the peace: it has actually begun to do so. 
Note the notion of objectivity, of reasonableness: "to cause fear, on reasonable grounds." One must therefore place oneself, and that's what the court would do in a trial for unlawful assembly, in the place of a reasonable person. Does he or she have a reason to fear?
In petto: I doubt a court would consider moving an orange cone to be frightening behaviour to those in the neighbourhood.
Note also that, as in any criminal proceedings, the burden of proving what constitutes the offence (the elements given here in the definition) and the intent of the accused persons lies with the prosecutor. Obviously, intent can be inferred from acts and gestures.
That is because unlawful assembly and riot are Criminal Code offences; they are crimes. They are not parking tickets: mens rea, or a culpable intent, must be proven.
Criminal law concerns individuals, not groups. Nobody can be convicted of unlawful assembly for taking part in a demonstration if they are not complicit in tumultuous behaviour or cause fear they will do so, especially if they don’t witness those behaviours .
Put simply, the fact of declaring a “demonstration illegal," a concept that is non-existent in law, does not give permission to arrest everyone.
Keep in mind that it will always be up to the courts of law to decide whether the accused participated in an unlawful assembly. The only performative utterance is "I find you guilty."
 Unlawful assembly is an offence that can only be prosecuted summarily, which means that the maximum penalty is a $5 000 fine or six months in prison.
 Riot is a crime punishable by a maximum of two years in prison.