LIFE WILL BE a lot easier for Rep. Marty Russo (D-Ill.) from now on. He won't have to fly around the country making a lot of tedious speeches in order to earn the $22,467 in outside income that the House rules allow. Instead, he has become counsel to a Chicago law firm, which will pay him $20,000 a year for his advice on a part-time basis. This is perfectly legal. The House rules do not prohibit members from practicing law, and about two dozen other members maintain affiliations with firms in their home districts. But it is not good practice.

Until recently, senators, too, were allowed to maintain law partnerships, and some went to great lengths to do so while avoiding a conflict with their legislative responsibilities. That's extremely difficult and led, in some cases, to such gyrations as the creation of a separate sub-firm excluding the senator in order to take cases where he might have a conflict. In 1977, the Senate wisely adopted rules that prohibit members from joining law firms or even allowing firms to use their names.

Mr. Russo is a member of the tax-writing Ways and Means Committee, and there is not a law firm in the country that does not have clients interested in the tax code. The committee is a minefield of potential conflicts for a legislator who also represents private clients. Mr. Russo could, of course, make public the names of all his firm's clients and the details of their interests before the committee. At least then the public would be on notice -- as it is in the case of campaign contributors and honorarium payers -- about the relationship. Or he could refuse to give speeches, offer amendments, lobby colleagues or vote on matters where his firm's clients have an interest. But his constituents did not send him to Congress to sit out the big battles.

The sensible solution is to avoid the problem in the first place. Senators have learned to live without law firm affiliations. So can the few members of the House who still maintain them. The best way to avoid the charge that a congressman's legal clients are buying special representation not available to every constituent is to change the House rule and adopt the Senate restriction.