Washington ? President Bush agreed with great fanfare last month to accept a ban on torture, but he later quietly reserved the right to ignore it, even as he signed it into law.

Acting from the seclusion of his Texas ranch at the start of New Year’s weekend, Bush said he would interpret the new law in keeping with his expansive view of presidential power. He did it by issuing a bill-signing statement – a little-noticed device that has become a favorite tool of presidential power in the Bush White House.

In fact, Bush has used signing statements to reject, revise or put his spin on more than 500 legislative provisions. Experts say he has been far more aggressive than any previous president in using the statements to claim sweeping executive power – and not just on national security issues.

“It’s nothing short of breath-taking,” said Phillip Cooper, a professor of public administration at Portland State University. “In every case, the White House has interpreted presidential authority as broadly as possible, interpreted legislative authority as narrowly as possible, and pre-empted the judiciary.”

Signing statements don’t have the force of law, but they can influence judicial interpretations of a statute. They also send a powerful signal to executive branch agencies on how the White House wants them to implement new federal laws.

In some cases, Bush bluntly informs Congress that he has no intention of carrying out provisions that he considers an unconstitutional encroachment on his authority.

“They don’t like some of the things Congress has done so they assert the power to ignore it,” said Martin Lederman, a visiting professor at the Georgetown University Law Center. “The categorical nature of their opposition is unprecedented and alarming.”

The White House says its authority stems from the Constitution, but dissenters say that view ignores the Constitution’s careful balance of powers between branches of government.

“We know the textbook story of how government works. Essentially what this has done is attempt to upset that,” said Christopher Kelley, a presidential scholar at Miami University in Oxford, Ohio, who generally shares Bush’s expansive view of executive authority. “These are directives to executive branch agencies saying that whenever something requires interpretation, you should interpret it the way the president wants you to.”