Quite right. Police officers are one of the only groups of people who don't have to pass through security to access the airside areas. After all, what are security going to say ? "excuse me officer but you appear to carrying a heckler and koch MP5 sub-machine gun, a side arm, 5000 rounds of ammunition and german shepherd with sharp teeth"
Police officers are trusted individuals and as such we let them carry deadly weapons because, in the main, they enjoy our confidence to use them responsibly. Strangely, the flight deck crew, in possession of an aircraft filled with hundreds of tonnes of flammable material capable of killing thousands, a missile if you like, still routinely have parts of their lunch confiscated by security because if several parts of the said lunch were mixed together they could create some kind of bomb, other than the readily available flying missile there were piloting that day of course.