IT HAD NEVER occurred to us that President Carter's friend and adviser, Charles Kirbo, was subject to the federal conflict of interest laws. But once Attorney General Griffin Bell explained the situation to the public the other day, as he had to Mr. Kirbo back in November, it made good sense. Mr. Kirbo, if he were so inclined, could use his influence - as, perhaps, the President's closest confident - to help himself or his clients. And that is what the conflict of interest laws were designed to prevent.

The idea that such a conflict could exist had occurred to us as it had to many others. Indeed we have been leery for some time of unofficial presidential advisers for just that reason. And we have had suspicions upon occasion in the past that actual conflicts of that type had arisen in the White House particulary when government policy changed in a way that seemed beneficial to someone close to the president. But the problem appeared to have no solution, unless a president cut himself off from all advice except that of members of his official family. And feq presidents want to do that, since there are advantages in maintaining some ties to old friends in private life.

Mr. Bell, however, did something taht no one in prior administrations seems to have done. He looked up the law. Then he told Mr. Kirbo that he is a "special employee" of government every time he gives the president advice. And as a special employee, even without pay, Mr. Kirbo is barred form providing advice on any matter in which he or his law firm has a financial interest. There is, Mr. Bell explained, "no such thing as a friend" who advises the government.

The difference this makes may or may not be substantial, depending upon the senstivities of a president and his advisers. But it is good to have the matter out in the open and to have a recognition, at least by this administration, that the conflict of interest laws apply to all those, appointees or friends, who advise a president.