When I search for "law and human behavior"
(with quote marks) on Google, I get only 106,000 hits. When I search for "law and human behaviour"
(again, with quote marks) I get 25,200,000 hits.
I don't have any prejudices about the American vs English spelling, but the journal is really called "law and human behavior" (see http://www.springer.com/psychology/psychology+%26+law/journal/10979). Furthermore, a search for the word "behavior" returns about twice as many hits as a search for the word "behaviour".