¹I believe there are some exceptions, like having contributed only an insignificant fraction of the whole work.
Let's say you contributed 500 lines of code to some project. You sue somebody for violating GPL and not publishing their changes. The judge has to give them the choice : either pay damages or actually comply (another western legal principle : money buys your way out of anything, as long as it isn't criminal).
What damages to assign ? Well, seems reasonable to say "how much for 500 lines of code ? A week's wages ? Okay, 2500 dollar damages awarded". The other party might become scared because other developers could conceivably sue, but ...
1) are only available either during a trial or as a last resort (if you can make a good case the defendant won't pay even if the judge compels them)
2) you'd still have to prove more damage will be done if injunction isn't there. Those have to be real damages, with real monetary amounts on them.
This is western law, it's practical. Anything you do that either doesn't bother anyone, or you prevent damage from occuring is legal, no matter how much it is against (civil) law.
The fact that something violates copyright, by itself, is not sufficient to get anything done in court at all.