Before doing anything else (other than contacting a firearms attorney), I suggest a careful reading of the CT law.
IS he, in fact, in violation? Several of the assault weapon laws passed back in 94 were virtually direct copies of the Federal law, without the sunset provision.
You need to check the wording carefully, to see if he is actually in violation. Some of the laws ban certain guns by name, from the date of passage of the law, or require registration from the date of enactment. Others are different.
I don't know which way CT law goes, sorry. He me be legal to own the gun, the gun may have been grandfathered, he may be only in violation of the registration timetable, there are several possibilitites.
THere are really only two courses of action, though. OK, three if surrendering the gun is an option.
1) continue to risk getting caught, and try to get the gun out of the state (not recommended)
2) Contact a qualified firearms lawyer (the NRA might be of some help locating one), and follow their advice. (recommended)
3) Do as the nice policeman says, and give it to him, so he can have it destroyed. Bow and scrape enough, and they might not even charge you with the crime, if they are feeling generous.....
Seriously, to stay within the law, get a lawyer, and let them represent you.
anything else is a risk, of one degree, or another.
After you get it resolved, be sure to thank those politicians, and your friends and neighbors who elected them, in an appropriate manner for bringing such joy into your life.