EVERY NOW and then Congress is faced with a politically charged and highly technical problem that it tries to resolve by appointing a commission to make recommendations to it and even to draft possible legislation. This course was taken, for example, when the Social Security system needed to be revamped. The really difficult choices were made by commissioners and subsequently adopted in legislative form by Congress.

A variation on this method was attempted in dealing with a restructuring of federal criminal sentencing, but because Congress did not actually enact the commission's recommendations (they became law in the absence of vetoing legislation signed by the president) the new sentence system has come under fire. Last week, two judges in the U.S. District Court in San Diego ruled that the sentence guidelines are unconstitutional.

It is easy to understand why the task of devising sentences was best assigned to a panel of experts who could give over many months to it. Sentence guidelines are meant to eliminate disparity in penalties for similar crimes. To write guidelines, every federal crime must be assessed and assigned a numerical value. This must also be done for aggravating and mitigating factors relating to the offense. The commission created by Congress was independent but "established in the judicial branch" and it included three federal judges. That did bring the required expertise to the panel, but it also muddied the line between legislative and judicial functions, and that eventually led the San Diego judges to invalidate the law.

Could this confusion have been avoided? Yes, because when the guidelines were ready, Congress could have put the whole package in a bill, passed it and sent it on to the president for signature. That can still be done, but somehow that obvious solution has been ignored on the Hill.

Originally, legislators feared that if the guidelines were brought to the floor, there would be considerable tinkering and amending and perhaps a fight over capital punishment -- a controversy that the guidelines avoid. But these considerations must be reassessed in light of this first court ruling on constitutionality. Plea bargaining and sentencing in connection with any crime committed after last Nov. 1 -- the day the guidelines went into effect -- are surrounded by uncertainty and subject to court attack until this constitutional question is resolved. It will take many months -- perhaps years -- for the Supreme Court to resolve it. Congress could take care of the problem immediately, and should.