Mutual trust is at the heart of the European Union. Although the Union lacks a general mechanism to enforce its rules and decisions, member states usually comply with them. This remarkable fact can in part be explained by self interest: although individual rules and decisions may be found harmful and are ducked from time to time, all member states know they win by sticking to the rules of the game. The member state that grudgingly applies a rule or a decision, trusts all the others to do the same most of the time. If this were not so, the system would break down, in spite of the European Court of Justice denying the rule of reciprocity legal status in the Union.