Which parts of their actions should be protected by law? They stopped doing their job, interrupted the work of others, and were in parts of the building that they did not leave when asked. These would normally be completely normal to treat with disciplinary actions and in the last case, they are trespassing.

Just adding in the 'but they were protesting something' doesn't change this by default. And even in Europe (where I'm from and still live) their actions would not be protected. They wouldn't get fired, but they would face some repercussions until they protest in a manner compatible with the law.

I cannot simply say "I'm not going to do any work, because I don't like that my company makes software used by the Metropolitan Police" and expect my company to say "fine by us, we'll keep paying you".