EDITORIAL : MILITARY AFFAIRS; PENTAGON MUST ADOPT MORE REASONABLE AND CLEARER RULES ON SEX.

IF there is one thing that most Americans won't stand for, it's an official double standard.

So for that reason alone, Air Force Gen. Joseph Ralston is unfit to serve as the next chairman of the Joint Chiefs of Staff.

After all, the Air Force hounded 1st Lt. Kelly Flinn out of the service after she had a relationship with the husband of an enlisted servicewoman. Making an exception to the military's prohibition on adultery for the benefit of Ralston, who had an affair 13 years ago while he was separated from his wife, would be totally wrong.

Granted, the circumstances were somewhat different. Flinn, according to the Air Force, was guilty of even graver misconduct when she defied orders to end her affair. But that in no way excuses Ralston.

Attempts made by Ralston's defenders to rationalize his conduct serve a useful purpose in one respect: They illustrate the need for the military to spell out more clearly what is inappropriate sexual conduct.

The big problem is the fuzzy status of adultery under military law. ``The military does not worry about adultery for the sake of worrying about adultery,'' Pentagon spokesman Kenneth Bacon said last week. ``It worries about adultery as it affects an officer's or enlisted person's ability to carry out a job.''

That may make sense to people in power, but we doubt whether the public is prepared to buy it. The standard expressed by Bacon simply is too subjective, and thus can be used selectively. And it certainly didn't protect Ralston, either.

So what's the answer?

We don't believe that the armed forces should try to solve the problem by enacting stricter regulations against sex outside marriage. That would be unrealistic and make criminals, in a military sense, of countless capable and reliable members of the armed services.

Likewise, it would be a mistake for the military to go to the opposite extreme and accept loose civilian attitudes about consensual sex. That indeed could adversely affect discipline and create morale problems for members of military families who must endure long periods of separation.

A group called the Defense Equal Opportunity Council's Task Force on Discrimination and Sexual Harassment has come up with some principles that seem applicable to the adultery question as well. They are (1) that policies ``must be clear and unequivocal'' and (2) definitions ``must be unambiguous.''

The military needs to do something along those lines to deal with the adultery problem. That's because no one deserves to benefit from a double standard - or be blind-sided for doing something that others with more influence got away with.