[ST17-002] - Trafalgar Law (Starter Deck 17: BLUE Donquixote Doflamingo)

Can I use this [On Play] effect to return 1 of my Characters to my hand even if my Leader does not have the {The Seven Warlords of the Sea} type?

Yes, you can. In this case, you cannot return 1 of your opponent's Characters with a cost of 4 or less to their hand.