I agree with your “You can’t just decide to take the law into your own hand” when doing so hurts or damages someone else. So I would agree with you not being able to hold someone detained in an unofficial jail just because they stole from you, or not being able to physically hurt someone that hurt you unless it’s self defense (so you do that to stop them from hurting you as they’re doing that). However, in cases like this, where you feel that the law is somehow unfair and needs to change, and you breaking it doesn’t actually hurt anyone, it feels like civil disobedience to me. So sure, there are consequences and you need to be ready to face them, but one possible outcome is your case helping change the law after all. A lot of progress has been made in democracies with that method.

Just think that if people would never take the law in their hands some countries would still have legal slaves, or legal segregation.