It works differently in different places. In Spain the release clause seems to protect the club (in the case of Messi's and Ronaldo's huge release clauses), so that if the player wants to leave before his contract ends, the club is under no pressure to sell. Of course, if the release clause is met AND the player wants it, they can't really do much.
In this case the release clause seems to protect Ba, as Newcastle got him on a free transfer after Ba had activated a previous release clause at West Ham after they were relegated.
