Correct.

For the benefit of u5a1a1 who is here defending the law even though he doesn't seem to understand how it works, I'll explain.

Per state law, anyone who possessed 16+ round magazines prior to 1 July 2013 could legally keep them.  But no one is legally allowed to acquire 16+ round magazines after that date.  

How does LE determine if the magazine was acquired before or after 1 July 2013?  They really can't.  Unless the person confesses he/she acquired it after 1 July 13, the cops have no way to determine if the magazine is legally or illegally owned.