The law has been clear: a clause in a contract imposing a penalty for breach of contract was unenforceable. What was completely unclear was (1) what amounted to penalty and (2) whether the rule applied beyond the payment of money following a breach of contract. For many years the accepted formulation was that if contract term provided for a payment which was "more than a genuine pre-estimate of loss" it would be an unenforceable penalty; otherwise it was a legitimate "liquidated damages" clause and not a penalty. In more recent years more complex cases have tested the rule, involving more than a straightforward payment for non-performance. the trend seemed to suggest that any clause whose effect was intended to be deterrence rather than compensation was potentially vulnerable to attack as a penalty.