A shake-up of dozens of Air National Guard (search) units has emerged as the most contentious part of the Pentagon's proposal to close or restructure hundreds of military bases across the country.

States are suing over the issue. Lawmakers in both parties are griping. And the independent commission reviewing the sweeping proposal has serious concerns about the impact of Defense Secretary Donald H. Rumsfeld's (search) Air Guard plan.

A major question about that plan also remains unresolved just weeks before the commission's September deadline to send its recommendations to President Bush, himself a stateside Vietnam-era pilot in the Texas Air National Guard (search): Does the law even allow the Pentagon to move Air Guard units without the consent of state governors, who through their adjutants general share authority over the units with the president?

"The Air Guard issue has become the long pole in the tent," said Christopher Hellman, a base-closing expert at the Center for Arms Control and Nonproliferation, a national security policy group.

In May, Rumsfeld proposed shutting or consolidating 62 major U.S. military bases and hundreds of smaller facilities, prompting lawmakers and communities to feverishly lobby the commission to spare their hometown facilities.

Only a fraction of the $49 billion Rumsfeld says his plan will save over 20 years would come from the Air Guard reorganization. But the impact on the Air Guard would be dramatic.

With roughly 106,000 members, the Air Guard currently has units stationed at about 95 Air Force bases and separate Air Guard installations and on leased land at about 78 civilian spots, including local airports.

Rumsfeld's proposal would shift people, equipment and aircraft around at least 54 sites where Air Guard units are stationed. Roughly two dozen sites would grow. About 30 are slated for closure or downsizing. In many of those cases, units would continue to exist but no planes would be assigned to them.

The Pentagon says the Air Guard changes are part of an overall effort to reshape the Air Force "into more effective fighting units" by consolidating a force that is now "fragmented into small, inefficient units."

Lawmakers, states and commissioners worry about the potential impact of the Pentagon proposal on recruitment, retention and training, and question whether the Air Guard will be able to fulfill its homeland security mission.

Anthony Principi, the commission's chairman, has appealed to all involved groups "to work to a solution that best serves the interests of our national security and our country."

"The commission believes a solution is needed," Principi told defense officials last month. However, he said, throwing out all of Rumsfeld's Air Guard recommendations would be "irresponsible."

Principi has since scheduled an Aug. 11 hearing to address the Air Guard plan.

Lt. Gen. H. Steven Blum, the Army general in charge of the National Guard Bureau, told lawmakers he's committed to ensuring each state has at least one Air Guard flying unit.

"If I don't have a flying unit in a state or territory, very shortly thereafter I will have no Air National Guard in that state or territory," he said.

Comments like those don't ease the fears of states — and lawmakers — facing losses.

"This doesn't work," Rep. Joe Schwarz, R-Mich., told Air Force officers at a recent House Armed Services Committee hearing.

"This thing is amazing in its incompleteness and in the disruption that it's caused, the insecurity that it has caused. And, I'm just, frankly appalled," added Rep. John Kline, R-Minn.

Pennsylvania was the first state to sue to try to stop the Pentagon. It's concerned about the fate of the Pennsylvania National Guard's 111th Fighter Wing, which is stationed at the Willow Grove Naval Air Station that the Pentagon wants to close. Illinois quickly followed with a lawsuit arguing that the federal government is out of bounds because it failed to consult the states. Other states may join those suits.

"Unless the commission wants to see the entire process held up by a legal recourse ... my guess is that in all likelihood the Air Guard bases are going to be removed from the list" of proposed closures, said P.J. Crowley, a Clinton administration military adviser who now is an analyst with the Center for American Progress, a liberal think tank.

The commission's legal counsel has said relocating, disbanding or moving Air Guard units from one state to another could be outside the commission's authority. The Pentagon wants the commission to wait for a Justice Department opinion before changing Rumsfeld's plan.

Maj. Gen. Roger Lempke, president of the Adjutants General Association of the United States, said the Air Guard plan is "beyond the scope" of the law authorizing the first round of base closings in a decade. He said the law "pertains to installations, not to units, unit equipment, people or positions."

Lt. Gen. Stephen G. Wood, an Air Force deputy chief of staff, said, "We believe that we are within the full extent of the law."