President Bush has asserted that he is not necessarily bound by the bills he signs into law, and yesterday a congressional study found multiple examples in which the administration has not complied with the requirements of the new statutes.

Bush has been criticized for his use of "signing statements," in which he invokes presidential authority to challenge provisions of legislation passed by Congress. The president has challenged a federal ban on torture, a request for data on the administration of the USA Patriot Act and numerous other assertions of congressional power. As recently as December, Bush asserted the authority to open U.S. mail without judicial warrants in a signing statement attached to a postal reform bill.

For the first time, the nonpartisan Government Accountability Office -- Congress's investigative arm -- tried to ascertain whether the administration has made good on such declarations of presidential power. In appropriations acts for fiscal 2006, GAO investigators found 160 separate provisions that Bush had objected to in signing statements. They then chose 19 to follow.

Of those 19 provisions, six -- nearly a third -- were not carried out according to law. Ten were executed by the executive branch. On three others, conditions did not require an executive branch response.

The instances of noncompliance were not as dramatic as some of the signing statements that have caused the most stir, such as Bush's suggestion that he was not bound by a ban on torture in U.S. military detention facilities. But congressional aides said they were significant...