I've heard from a couple of different people in recent days, including a local LEO that I tend to trust, that the NYS ban on high capacity magazines was lifted last year. My LEO friend said that the ban still affects "assault weapons," but not handguns anymore. He indicated that while he used to get hi-cap mags marked "Law Enforcement Only," every hi-cap mag he's gotten in the last year did not have this stamp on it, presumably because it doesn't matter anymore.
In my research so far, I have been unable to find any indication that NYS's ban on high capacity (over ten rounds) magazines was ever lifted. I believe he is mistaken, and I suspect he is confusing NYS's ban with the expiration of the federal assault weapons ban.
Maybe someone can fill in the details but from your description I presume that he is talking Glock mags. I am not going to try to explain the details of the "law Enforcement Only" because i don't know all of them other than it has nothing to do with the ban being lifted. It hasn't.