Arguments heard on special prosecutor law. SUPREME COURT

The nation will get a 90-minute course in constitutional government today when the Supreme Court hears oral arguments on Morrison v. Olson, the much-heralded case involving the constitutionality of the independent counsel law. How the justices eventually rule could have broad significance for the concept of separation of powers, particularly in terms of presidential autonomy.

At issue is appointment of independent counsels by a three-judge federal panel under the Ethics in Government Act, rather than by the United States attorney general.

In January, the US Court of Appeals for the District of Columbia struck down the special counsel provision of the 1978 act in a 2-to-1 ruling. The majority held that the law violates the constitutional doctrine of separation of powers.

Equally at stake is the practical matter of the future of several current probes by special prosecutors appointed under provisions of the 1978 Ethics in Government Act. This case has strong implications for the Iran-contra investigation being conducted by special counsel Lawrence Walsh and for the four men - Lt. Col. Oliver North, Adm. John Poindexter (ret.), Maj. Gen. Richard Secord (ret.), and businessman Albert Hakim - against whom he has obtained indictments.

It has direct bearing on the investigation of former US Assistant Attorney General Theodore Olson by special counsel Alexia Morrison, who is the named counsel in the Supreme Court case.

Although Mr. Walsh also accepted an appointment as special counsel from the attorney general, if the law is ruled invalid it might be argued that evidence he gathered before this parallel appointment should be thrown out. Ms. Morrison did not accept a parallel appointment from the attorney general.

A negative ruling also could affect the recent perjury conviction of former White House deputy chief of staff Michael Deaver.

Although the highest US judicial tribunal is supposedly immune from political considerations and public opinion, at least some court observers believe that the justices will be acutely aware of the present controversy that swirls around Attorney General Edwin Meese III, who is the subject of an investigation by special prosecutor James McKay. Mr. McKay accepted a Justice Department as well as court appointment.

``Of course, the Supreme Court should never respond to public pressure,'' political historian James MacGregor Burns says. ``But there is a fundamental issue of credibility and integrity. ... There is today a tremendous suspicion of government and [government] secrecy. It must be remembered that the Supreme Court is the guardian of the integrity of the country,'' Professor Burns points out.

Others insist, however, that even if the independent counsel provision is struck down by the court, investigations into alleged wrongdoing in Iran-contra and other matters will continue.

``The criminal process will go forward,'' says Heritage Foundation fellow and constitutional scholar Bruce Fein. ``This should [assuage] public concerns.''

But Mr. Fein says he believes that the justices will ``throw out'' the special prosecutor provision as it now is written.

Georgetown University law professor Mark Tushnet agrees that the Iran-contra investigations will proceed even if the special prosecutor statute is struck down.

But Professor Tushnet, an authority on separation of powers, says he believes that the Supreme Court will uphold the law - relying on a provision of Article II of the US Constitution that allows Congress to ``vest the appointment of such inferior officers, as they think proper, in the President alone, in the courts of law, or in the heads of departments.''

This is a core legal dispute in the case. Walsh and Morrison contend that they are ``inferior officers'' appointed by ``courts of law'' under congressional authority - and hence their status is constitutionally sound. The appeals court, however, ruled that they are ``officers of the United States'' who must be nominated by the President. This set up the current appeal.

If the Supreme Court were to uphold this decision, it would mean that all criminal investigations and prosecutions of high-level government officials could be conducted only by the Justice Department or by special prosecutors specifically appointed by the White House.

It is noted that when the Iran-contra affair began to surface both President Reagan and Attorney General Meese asked for the appointment of an independent counsel. This, some believe, could undercut the argument that the president's power is invaded by the independent Iran-contra probe.

The Supreme Court has not been entirely consistent in its interpretation of the separation-of-powers doctrine, at times allowing Congress or the courts to encroach on executive power. But in the well-publicized Gramm-Rudman dispute, the court said that federal lawmakers could not designate to one of their employees the duty of cutting the budget under a deficit-reduction law.

``There are many examples [in government] where there is a crossover'' says Arthur Goldberg, a former associate justice of the Supreme Court. ``The president is supposed to conduct foreign policy, but Congress can frustrate him by denying appropriations.''

Though insisting that ``separation of powers is a grand constitutional principle,'' Professor Burns says: ``These questions must be settled in terms of the practical needs of the situation.''