McCain opted into the federal campaign financing system when he was too broke to continue his campaign without it. Now he has exceeded the limit of funds he was allowed to spend before the Republican convention, but has he stopped collecting and spending money?
And every dollar he spends above the cap is a crime.
McCain's excuse for his criminal behavior is that after opting in to the system and using it to get a loan to continue, he later announced that he was opting out.
The similar behavior of a bank robber would be to claim that when he told the bank clerk to hand him all the money or he would kill her he had his fingers crossed behind his back and didn't really mean it, and besides, the clerk didn't give him the money anyway.
Fair courts wouldn't buy either argument.