Sharpie rule 

This universal law states that if one steals a Sharpie marker pen from a colleague's pencil case, it will become the thief's possession once the thief has owned it for longer than the original owner.

"He stole my new Sharpie marker but I can't take it back because of the goddamn Sharpie rule."

Sharpie rule by blindorange October 2, 2009