Similar to terms like Mr Tickle fingers or the Knee-grab Crab, being "the butt police" involves running after other people making a 'whoo-whoo' siren-like noise and holding grabbing hands out in front of you giving the impression you are going to grab a person by the rear end.

The term was coined by Detective Butt Sergeant Paul MacMillan of Preston, England who regularly makes attempts to arrest his small children resulting in screams, giggles and avoiding capture.
"Oh-oh, you better watch out or the butt police will catch you.... WHOO-OO-OO-OO!!"
by GoggleboxUK November 28, 2018
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The police who enjoy shoving things up your anoos.
BWOOP BWOOP!! Butt Sex Police alert, stick it in his anoos!
by Butt Sex Police February 24, 2005
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