At least 13 House members belong to National Guard or military reserve units, but they can't be called to active duty for the current Iraq crisis unless they first give up their seats.

Any time there is a mobilization of Guard and reserve units, the Pentagon automatically puts members of Congress and other top government officials who are reservists or guardsmen on standby. "Their name is in a computer; that's about all it amounts to," said a congressional aide who asked not to be identified.

Rep. Dave McCurdy (D-Okla.), a captain and member of the judge advocate's corps in the Air Force Reserve, said lawmakers weren't likely to resign for a limited call-up.

"If there is an acknowledged war and the entire nation is mobilized," McCurdy said, "I think we'll all go."

Seven of McCurdy's colleagues are in the reserves and five more are active in their state National Guard units. All fall under federal guidelines that require officials in line of succession to the presidency, members of Congress and other key officials to transfer from ready to standby reserve status.

They may participate in drills and training exercises, and collect points for retirement pensions. But they cannot be paid or activated.

Since the Civil War, presidents and members of Congress have recognized an inherent conflict in having lawmakers who exercise civilian control and oversight of the military simultaneously serve under military commanders.

President Lincoln prohibited his generals from allowing lawmakers to join them in combat after his friend Sen. Edward Baker (R-Ore.) crossed the Potomac to take part in the Battle of Balls Bluff and was killed.

Denied a leave of absence for a second tour of duty in World War II, Republican Henry Cabot Lodge of Massachusetts gave up his seat in Congress in 1944 to join the fighting in Europe. He had been granted one Senate leave, to serve in 1942 with American tank crews in North Africa.

But after other lawmakers -- including a then-junior House Democrat from Texas, Lyndon B. Johnson -- demanded "cameo appearance" tours, the War Department in 1943 stopped activating sitting members of Congress.

"It's a pretty basic conflict of interest," said Senate Historian Richard A. Baker. "It was inconveniencing a lot of people and there was a big concern that a lot of it was being done for political considerations."

There was also the concern that services would use reserve promotions to reward legislators for shepherding projects or weapons systems through the complex authorization and appropriations webs of Congress.

"I don't think in this day and age that you can serve two masters," said Rep. Bill McCollum (R-Fla.), a Navy Reserve commander.

List of Lawmakers in Guard Reserve

The members of Congress known to be active members of reserve or National Guard units:

Rep. Thomas R. Carper (D-Del.), commander, Navy Reserve.

Rep. Bob Clement (D-Tenn.), lieutenant colonel, Tennessee National Guard.

Rep. Chuck Douglas (R-N.H.), colonel, New Hampshire National Guard.

Rep. Claude Harris (D-Ala.), lieutenant colonel, Alabama National Guard.

Rep. H. Martin Lancaster (D-N.C.), commander, Navy Reserve.

Rep. Greg Laughlin (D-Tex.), lieutenant colonel, Army Reserve.

Rep. Bill McCollum (R-Fla.), commander, Navy Reserve.

Rep. Ronald K. Machtley (R-R.I.), commander, Navy Reserve.

Rep. Dave McCurdy (D-Okla.), captain, Air Force Reserve.

Rep. Timothy J. Penny (D-Minn.), lieutenant junior grade, Navy Reserve.

Rep. Steven Schiff (R-N.M.), lieutenant colonel, New Mexico Air National Guard.

Rep. Gerry Sikorski (D-Minn.), lieutenant, Navy Reserve.

Rep. John S. Tanner (D-Tenn.), lieutenant colonel, Tennessee National Guard.