I'm going to try to clear a "lil' sumthin'" up.
LEO's and Mil. may "possess" restricted mags. ie. they may "have them on their person" while performing their official function. ie. at work, or whle working. So, the feds can't "lock up" LEO/Mil types while they are performing a state/fed sanctioned function. Banning these mags/weapons from LEO/MIL use, would make it very difficult for them to function.
It does not make it legal for LEO/MIL to "own" ANY mag. Only those they can articulate are necessary for work, ie. those issued w/ for their issued arms.
So being a LEO/MIL, would allow one to carry/have certain mags that they need while working and or performing a work function, off duty for agencies that allow off duty MOS to carry obviously is covered, or MIL members travelling that happen to possess M16 +10 rndrs. as well. But an LEO w/ Posty AR mags, if their dept. doesn't require them to use an AR, may very well have problems. A MIL. member, w/ +10 Glock mags could have a problem. Now, is it possible for a fed type to overlook a trained pro. mil or LE that knows the benefit of protecting themselves and their family adequately? Sure, I've seen it. But, beware, its not automatic or legislated.