Vladimir_Berkov:.. because law enforcement is exempt from all gun control measures...
This is patently untrue.
Even Kalifornia, one of the most notoriously "anti" states as far as civilians are concerned, has strict laws regulating what, when and where LE can purchase and use weapons.
Cops there have a 15 day wait if they buy a gun for personal use, just like civilians.
PDs have to justify/register their purchases of machine guns, suppressors, and DDs with ATF, just like we do.
They are sometimes exempted from the transfer taxes.
Law enforcement use of heavy weapons like grenade launchers and .50M2 Browning rifles is not always justifiable, but there are places where they are handy and much needed.
40mm Grenade launchers can lob tear gas canisters and smoke as well as explosives and frag. Mil surp gas and smoke canisters are inexpensively available through the DRMO, and can save a department beaucoup bucks that they can spend on other programs, and gear. The 38mm civilian tubes are more expensive to feed.
A fifty can allow you to punch through a hard target like an armored car or reinforced concrete barricade.
Bear in mind that the forward thinking departments obtain this gear with the "Better to have it and not need it, than need it and not have it" perspective in mind.
Don't ask ME why you can't have something in your state, ask your legislators.