A moral logic question

Suppose You find a loophole in legal law (whatever that means), and commit an act which is considered morally wrong,but in such a way that it is acc. to law.
Now the country court finds the loophole, and changes the law in such a way that the loophole is taken care off, and acc. to new law the act committed by you was illegal.
Now you are caught by the police. In the court hearing you are asked to confess,if you dont confess and found guilty you will be heavily punished,and if you confess you might be pardoned to some unknown extent.



Will you confess?
and in any case Is the court wrong in punishing you?