You absolutely can do that morally and legally. I'd say you're even required to morally. Laws are written by those in power and therefore meaningless. Any new ruling class or clique can make their own ones.

There is nothing modern about your society which forces humanity down the drain. And the way you're talking about modern society, law and social contract bullshit you definitely sound like a liberal. Or are you gonna tell me you're a fascist with a thing for liberal capitalism and personal rights?

By the way it's quite hypocritical to oppose violence only when your preferred ideology is in power. But before that or under other systems it's of course fine to topple and fight and oppose them violently. One day violence may no longer be necessary, but in today's world it still is.