Yet the state of South Carolina is doing precisely that. As The State newspaper reported Monday, though the state exempts from taxation part-time income Guard and Reserve members draw for attending monthly drills and two weeks of annual training, it does tax the active-duty income they receive when called up for service at non-combat installations.

That taxation applies to South Carolinians guarding al-Qaida and Taliban prisoners at the Guantanamo Bay (Cuba) base. Technically, that's not a combat zone. But you don't have to serve in Iraq or Afghanistan to fulfill an important -- even risky -- role in America's defense.

The state taxation on last year's income will hit many Guard and Reserve members all at once. The U.S. Defense Financial Accounting System has not been deducting state-tax "contributions" from South Carolinians serving in the Guard and Reserves.

The reality that a significant number of them now face a steep tax bill that they wouldn't have owed if their status hadn't changed from part-time to active duty sends a troubling signal to our current -- and potentially future -- citizen-soldiers.

Sen. Wes Hayes, R-York, wants to solve this problem with the "Citizen-Soldier Tax Relief Act," which would exempt from state income tax Guard and Reserve members called up for federal active duty. As Sen. Hayes, a colonel in the S.C. National Guard, put it: "I think it's a small benefit that we can give to people who've been taken out of their daily lives and put into harm's way."

Other states with similar situations are considering similar proposals. Some arguments against such legislation: All members of the armed forces, including the Guard and Reserve, must pay federal income taxes if not assigned to a combat zone. Those who enlisted in the full-time armed forces are subject to state income taxes. And this or any other state must weigh any reduction of tax revenue carefully.

But the National Guard and Reserve now face increasing demands, and retention of those forces is of the utmost national interest if the United States is to maintain its extraordinarily effective, all-volunteer armed forces. Incentives for joining the military -- including the "regular" military and the Guard and Reserves -- must keep pace with the challenges we face in the war on terror.

And if pay for part-time Guard and Reserve duty is exempt from taxation in this state, pay for active-duty Guard and Reserve duty should be exempt, too.