I gave a engagement ring to my Girlfriend, am I allowed to ask for it back ?

In New Jersey, an engagement ring is considered a conditional gift, conditional upon there being a marriage. Furthermore, NJ is also a "no-fault" state, so I don't think it would matter whether you or your fiance were the person seeking to stop the marriage. So I believe you can definitely seek the return of the ring, even if you are the person seeking to break the engagement. However, if your fiance refuses to return the ring, you may need to file a law suit. The lead New Jersey case is Aronow v. Silver, an appellate division case decided in 1987.