There is nothing illegal about an after-market trigger anywhere that I know of - but it's always safer to check your state/local laws. If a district attorney is looking to make a name for himself, is anti-gun, or has a boss breathing down his (or her) neck, there's no way of knowing what piece of evidence will be used against you. A few years ago one man was unjustly imprisoned (his sentence later overturned) merely for his choice of firearm, a 10mm Glock. The DA made the jury feel since he chose such a high-power handgun his intent was to kill someone. The truth was he chose, as many do, to carry a firearm in line with what local LEOs carried. Any modifications you make to your carry piece can lead to a gun-ignorant community to believe whatever the DA says instead of common sense. While you shouldn't have to, it is wiser to carry a non-modified piece. Many DAs don't go after crooks because it's too much work. A law-abiding citizen's case is a slam-dunk for many of them. Be safe!