Federal agents continue to eavesdrop on Americans' electronic communications without warrants a year after President Bush confirmed the practice, and experts say a new Congress' efforts to limit the program could trigger a constitutional showdown.

High-ranking Democrats set to take control of both chambers are mulling ways to curb the program Bush secretly authorized a month after the Sept. 11 attacks. The White House argues the Constitution gives the president wartime powers to eavesdrop that he wouldn't have during times of peace.

"As a practical matter, the president can do whatever he wants as long as he has the capacity and executive branch officials to do it," said Carl Tobias, a legal scholar at the University of Richmond in Virginia.

Lawmakers could impeach or withhold funding, or quash judicial nominations, among other measures.

The president, however, can veto legislation, including a law demanding the National Security Agency obtain warrants before monitoring communications. Such a veto would force Congress to muster a two-thirds vote to override.

"He could take the position he doesn't have to comply with whatever a new Congress says," said Vikram Amar, a law professor at the University of California, Hastings, and a former Supreme Court clerk.

Douglas Kmiec, a former Justice Department official under former presidents Reagan and George H.W. Bush, speculated the younger Bush would assert executive authority to continue eavesdropping in the face of new legislation - perhaps leaving the Supreme Court as the final arbiter.

"He has as much a constitutional obligation to assert himself, just as much as Congress does," Kmiec said. "We do need an arbitrator, an interpreter. That's what the courts, the third branch of government, was intended to be."

On Dec. 17, 2005, Bush publicly acknowledged for the first time he had authorized the NSA to monitor, without approval from a judge, phone calls and e-mails that come into or originate in the U.S. and involve people the government suspects of having terrorist links.

Bush said he had no intention of halting what he called a "vital tool" in the war on terror.

When the Republican-controlled Congress adjourned last week, it left the spying program unchecked.

The next move falls to the Democrats who take control in January and are considering a proposal to demands Bush get warrants and others lengthening the time between surveillance and when a warrant must be obtained.

A spokesman for Sen. Harry Reid, the incoming Senate majority leader from Nevada, said the eavesdropping issue "is something he expects to tackle early next year."

"He doesn't believe in giving the president a blank check to listen to the phone conversations of millions of Americans," spokesman Jim Manley said.

Jennifer Crider, a spokeswoman for Nancy Pelosi, the San Francisco Democrat who will become House speaker, said eavesdropping legislation was under consideration and hearings on the topic were likely early next year.

Decisions are pending in dozens of lawsuits challenging the program.

The Cincinnati-based 6th U.S. Circuit Court of Appeals, the highest court squarely confronted with the issue so far, is to hear the American Civil Liberties Union's challenge Jan. 31. One stop short of the Supreme Court, the appeals court will review a Detroit judge's ruling that the program was unconstitutional.

The case is American Civil Liberties Union v. National Security Agency, 06-2095.

© 2006 Associated Press

###