Marty Lederman
discusses when a bill signed by the President is not a law.
The answer: When "Dennis Hastert has violated his constitutional oath by attesting to the accuracy of the bill, knowing that the House version was different (and having intentionally avoided fixing the discrepancy when it came to his attention before the House vote). And Stevens and the President are coconspirators, assuming they, too, knew about the problem before they attested to and signed the bill, respectively."