Soon fifteen is going to be an insufficiently low limit. Yes, slippery slope is generally a fallacy, but...it actually is happening. In Colorado, your "reasonable" magazine size limit is fifteen. In New York, it's ten in a pistol and five in a rifle, and you can only load seven rounds in the ten round magazine. California was a governor's veto away from banning all semi-automatic rifles with detachable magazines.

I also have yet to see a reason why these shouldn't apply equally to the police. If large capacity magazines only exist to kill people as quickly as possible, then why should the police have that? How many times are they going to encounter enough armed belligerents for the capacity to matter?