For the first time in the memory of National Guard officials, a state executive -- Gov. Joseph E. Brennan (D) of Maine -- has refused to send troops on previously scheduled maneuvers. Other states seem prepared to follow suit as a protest against Reagan administration policies in Central America.

"Many states are looking at it on a case-by-case basis," said National Guard spokesman Joseph G. Hanley. "Some have put restrictions on -- no large units, or no combat-oriented units -- but they might say fine for a medical unit."

In Maine and Massachusetts, Democratic governors barred any National Guard participation in future Honduras maneuvers. Their counterparts in Arizona, Washington, New York, Kansas and Texas have raised questions or placed conditions on participation. In Iowa, Oregon and elsewhere, the maneuvers have sparked fights between Democratic legislators and Republican governors.

Thousands of Guardsmen have been exercising with regular Army troops in Central America in recent years. The National Guard, unlike active-duty and reserve troops, remains under state control except during declared wars or emergencies, such as the Vietnam conflict. That control is giving some governors a rare opportunity to venture into foreign affairs, as an aide to New York Gov. Mario M. Cuomo (D) pointed out.

"He Cuomo said something along the lines of, 'I wouldn't want to see our National Guard troops used to further federal policies in Nicaragua,' " the aide said. "Is Honduras right next to Nicaragua? . . . I'm no foreign policy expert."

Cuomo has not been asked to send any troops. Some governors who have been asked find themselves torn between critics of administration policy, who urge a boycott of the maneuvers, and National Guard troops who want to go.

"I think a number of them were not very happy about it," Brennan said after he canceled a visit to Honduras by 35 combat engineers. "But in Maine there was a lot of support . . . . The mail ran 3-to-1 in favor."

Brennan said he ordered his troops to stay home primarily for their safety, but also because he disapproves of U.S. military involvement in Central American conflicts.

"Basically, I don't believe Honduras is a very safe place to train," he said. "Secondly, I personally do not happen to agree with our Central American policy. I think we're inching our way into another Vietnam."

Since the summer of 1983, tens of thousands of U.S. troops have built roads in Honduras, practiced parachuting, taught counterinsurgency techniques to Honduran soldiers and performed other tasks in months-long military exercises there. Administration officials say the maneuvers are intended to train U.S. troops, foster good will in Honduras and warn neighboring Nicaragua, where a leftist government is said by U.S. officials to harbor designs on its Central American neighbors.

This year, 5,350 Guardsmen will rotate through Honduras as part of those exercises, Hanley said.

"From our point of view, it's not a way to intimidate anybody or make anybody nervous," he said. "That's a key point. Everything that we're doing in Central America is training, training that's been authorized by Congress."

Maneuvers abroad offer the most realistic training for the part-time soldiers of the Guard, Hanley said, from shipping equipment to getting inoculated. Firing ranges and engineering projects are less "environmentally constrained" than in the United States, he added.

"If you're building a road, you don't have to worry about the width of the culverts, about the Environmental Protection Agency or about the environmentalists," he said. "Those are not concerns down there."

Guard leaders in some states have complained about their governors' policies, according to Hanley and some local officers, but they do so cautiously.

"I would never say the governor made the wrong decision," said Lt. Col. Donald Consolmagno, National Guard spokesman in Massachusetts, where Gov. Michael S. Dukakis barred participation. "He's the commander in chief, and we as good soldiers carry out the policies and directives of the commander in chief."

A spokesman for Dukakis said his directive was intended to protect the troops.

"These are citizen-soldiers, and they ought not to be placed into a potentially dangerous situation on alleged friendly training exercises," the spokesman, James Dorsey, said.

"If the U.S. wants to send troops into Central America, that ought to be something that the president asks Congress and the Congress debates and votes on . . . . Barring that, I don't think there ought to be this subterfuge of sending Guard units down from the various states."

Several Democratic legislators in Oregon made a similar argument. Republican Gov. Victor Atiyeh vehemently disagreed.

Since Guardsmen might be deployed to Central America in a war, Atiyeh's spokesman said, it would be "ludicrous and perhaps even life-threatening" not to train there.

"We don't want to put our boys at risk by denying them training in the kind of environment they would be placed in if, God forbid, they should be called into service," spokesman Denny Miles said. "Yet in this case, because there's a political brouhaha about Central America, it becomes a political issue."

Hanley said the Guard has had no trouble so far finding units for Honduras duty. If too many governors raise objections, however, the same units may have to return, which he said would be unfortunate.

As a result, he said, Guard leader Lt. Gen. Emmett H. Walker Jr. has invited any governor to follow the example of Texas Gov. Mark White Jr. (D) and visit the troops.

In the jungles of Honduras last year, White, the commander in chief of the Texas National Guard, donned borrowed combat fatigues and inspected his troops.

White was worried, an aide said, that the Reagan administration's unending round of military maneuvers in unsettled Central America might put his soldiers in harm's way. But his brief tour south reassured him.

"It turns out they were training in a remote, very impoverished area where the villagers were in need of all kinds of help," White's spokeswoman, Ann Arnold, said. "The relationship that was built up between the people in that area and the Guardsmen was heartwarming."

"We think perhaps they the governors might be making decisions without full knowledge of the complete set of facts concerning the situation," Hanley said. "We have an ethical obligation to give our people the best training we can."