No one becomes a member of the Supreme Court unless a President nominates him and until the Senate confirms him. Thus the potential for conflict of interest in always present.But it reached a peak level in the last term.

The court had to decide a case involving former President Nixon, who had put on the court four of its nine members: Chief Justice Warren E. Burger, and Justices Harry A. Blackmun, Lewis F. Powell Jr. and William H. Rehnquist.

None of the Nixon appointees disqualified himself from considering and deciding the case, which involved the constitutionality of a law giving government archivists control over access to the former President's papers and tapes.

Blackmun and Powell were among the seven justices who voted against Nixon, in a decision announced June 27. Burger and Rehnquist each wrote a strong dissent.

Earlier, the court had to act on petitions by Nixon's two top aides in the White House, H. R. Haldeman and John D. Ehrlichman, and John N. Mitchel, the Attorney General during most of the Nixon presidency. All wanted the court to keep them out of prison by agreeing to review their Watergate cover-up convictions.

Without explanation, as is customary, Rehnquist, who had been a top Justice Department official under Mitchell, disqualified himself in the matter, which was the fount of the notorious National Public Radio "leak" about how the justices purportedly had lined up in a preliminary secret vote.

That left eight justices. Review would have been granted if four of them had voted for it. All that's known is that fewer than four did so.

Behind the scenes, some lawyers entertained the notion of asking Burger and possibly other Nixon appointees to disqualify themselves. Burger, among other things, has been reported to be on some of the tape recordings in the Nixon papers case.

Nothing came of the idea, partly because of the Rule of Necessity, which has been traced back in English common law to 1430. The rule - akin to Harry Truman's "The buck stops here" - is that a judge is not disqualified to try a case because of his personal interest in the mater at issue if there is no other judge available to hear and decide the case.

The rule got a rare test in a case brought by 140 federal judges who claimed that their pay in real dollars had been unconstitutionally decrease 34.4 per cent by inflation in the 6 1/2-year period ended Oct. 1 1975.

The case was decided May 18 by seven judges of the U.S. Court of Claims. Being federal judges, they each had thousands of dollars at stake - just as did the plaintiffs. They resolved this potential conflict of interest against themselves and their robed brethen - 7 to 0 on the constitutional issue, 4 to 3 on a statutory issue.