Later courts may overturn a decision which was unconstitutional, yet mistakenly ruled constitutional by a biased Court. Every law is not constitutional once passed, signed, and approved.
They certainly can but until a new court rules differently the law is in place and enforced and by definition constitutional. Not right or wrong just that it had followed the constitutional process. Their is no criminal jeopardy against those that pass and sign laws within the boundaries of the process laid out in the constitution that the court deems unconstitutional. Some may argue that there should be but the Founders did not agree.
No, but it is enforcable law until ruled otherwise or repealed.