I believe that the bill was amended to exempt law-enforcement agencies. Personally, I think that the ammunition manufacturers should simply refuse to do business with any of them if this passes.
Hey, it worked in Maine - the AW bill was voted down after Bushmaster told the legiscritters that it would cut off LE if it could no longer sell its products in state. This is no different.
This, despite the fact that it would make more sense to require police to carry serialized ammo in their duty weapons than to require the general public to use such ammo. Police are more likely than normal persons to find themselves in a situation where more than one person is shooting at someone. Having serialized and tracked ammunition would make it easier to resolve such cases (including those where a stray round injures an innocent bystander).
Exempting police from such a requirement for their duty ammo while subjecting everyone else to such a requirement for their range ammo shows the real intention of the bill.