The trick is to categorize protestors as "domestic terroists", despite having not done any extreme violent actions, as the Canadian government seems to be doing here.

A "protest" that prevents people from crossing a border or shuts down a city isn't a protest. It is hostage-taking.

The US First amendment has some good language on this: the people have a right to peaceably assemble, and to petition the government for a redress of grievances. Imposing a blockade does not qualify. If they just sit in front of Parliament and hold up signs and shout, but don't impede anyone going about their business, then they have a right to make their voices heard.

But what about (some other protest)? Civil rights protesters are usually ordered to disperse after a short time and get arrested if they don't. Sometimes they engage in civil disobedience, but they can be arrested if they do that.