“They do need to be aware of that possibility,” he said.

Mr. Cooper, a member of the Army Reserve, said that he was taking part in training last week at Fort Huachuca in Arizona when the injunction was issued, and that he was surprised by the lack of visible opposition or outcry.

He likened it to a “giant shoulder shrug of ‘so what?’ ”

Most of the people he was with, he added, were younger members of the service, and “a few people actually thought repeal had already occurred.”

Cynthia Smith, a Pentagon spokeswoman, would not address a question about whether a recruit who volunteered that he was gay during the current suspension of the law might face expulsion from the military if the decision were appealed.

She called that situation hypothetical and said only that recruiters had been reminded that “they need to set expectations by informing the applicant that a reversal for the ‘don’t ask, don’t tell’ law may occur.”

An opponent of service by openly gay men and lesbians dismissed the Pentagon shift as “a political ploy.”

Elaine Donnelly, the founder of the Center for Military Readiness, a conservative organization that opposes gay service in the military, said Congress, under the Constitution, has the authority to draft rules for the military.

The Department of Justice, she added, acted properly by filing its request for a stay.

“There was no need to introduce this additional element of disconnect with the law and precedent and policy,” Ms. Donnelly said. “The military doesn’t need this  but this is what the Department of Defense did, and frankly, I find it inexplicable.”