A law enforcement round is any round law enforcement shoots.
In my 17 years as a L.E. officer, thats about the only logic I can come up with. An "L.E. only" round is usually a A.P. round that is designed to be fired from a handgun or sub-gun. There is a lot of l.e. only ammo out there for the fn5.7X28. There is some 9mm stuff that will penetrate level II vests. There is some .308 stuff that will defeat level IV ceramic. (Supposedly, I would have to see that to believe it.)