Being there was perfectly legal. Attending a riot can be a lot of fun. In fact, if everyone is well behaved, it's encouraged and called peaceful protest.
Everyone that entered did so illegally. The ones that stayed outside were perfectly legal, and are not part of the group that is still wanted by law enforcement.
Moreover, a riot is not a protest and even a protest isn't always legal (even in western countries where they are a fundamental right, i.e. an expression of free speech)