The Constitution does not allow Congress to "put the budget process on autopilot and turn the helm over to unelected officials," a lawyer opposed to the Gramm-Rudman-Hollings budget-balancing law argued yesterday in the opening round of an expedited federal court battle over the law's constitutionality.

That "abdication" of the lawmaking power is "not what the Founding Fathers had in mind . . . when they wrote the Constitution," attorney Alan Morrison, representing a group of congressmen, told a special three-judge panel during a three-hour hearing in U.S. District Court.

But Senate Legal Counsel Michael Davidson argued that Congress acted properly in passing the sweeping budget-cutting law. "The ultimate accountability" for budget cuts still "lies clearly with Congress," he told the judges.

About 250 lawyers, reporters and spectators packed the huge, rarely used, ceremonial courtroom at the courthouse for the formal beginning of the accelerated judicial review required by the law. The judges are obliged to rule as soon as they can, possibly within the next month or so. The case is then expected to go quickly to the Supreme Court for a final ruling before the high court's term ends in early July.

Under the controversial law, the annual federal budget must be balanced by fiscal year 1991. If Congress fails to meet the prescribed deficit target in any year, the key part of the law requires automatic, across-the-board spending cuts split evenly between defense and domestic spending. Three agencies -- the Office of Management and Budget, the Congressional Budget Office and the General Accounting Office, also an arm of Congress -- have a role in determining whether Congress has met the target and how it should be met.

The constitutional attacks, coming yesterday from Rep. Mike Synar (D-Okla.) and 11 other congressmen, represented by Morrison, the National Treasury Employes Union and the Justice Department, all focused on the automatic triggering procedure.

The challengers said the unique arrangement violates fundamental constitutional principles at the heart of our system of government, the principle that the three branches of government each have separate duties and powers.

Congress passes the laws, the executive branch enforces them and the judiciary resolves constitutional controversies, the challengers argued. Tinkering with the system of checks and balances could undermine the system, they contended.

Lawyers for Synar and the union emphasized that Congress gave away too much of its lawmaking power to "unelected bureaucrats" who, in effect, would undo prior laws appropriating money. They argued that the comptroller general, who heads the GAO, is a legislative employe and the law unconstitutionally gives him executive branch functions.

Assistant Attorney General Richard K. Willard, although also opposing the "trigger" mechanism, said Congress did not give away too much power; it simply gave it to the wrong person: the comptroller general.

Congress can only delegate that authority to the president or someone under the president's direct control, Willard argued, but the comptroller general is not accountable to the president. Willard said that under the law, the president would be the "mouthpiece of the controller general."

The president has no discretion in making the cuts -- something the House insisted upon in order to pass the bill -- but that violates the Constitution no matter for whom the comptroller general works, Willard said.

Davidson, joined by Steven R. Ross, general counsel for the clerk of the House of Representatives, argued that the judiciary should not immediately undo what Ross called an "emergency, temporary, measure."

Davidson argued there was no improper delegation of power by Congress to the GAO or to the president because the law strictly defines what each official is to do.

The president "has some flexibility," Davidson argued, and the comptroller general does not "issue an order to the president."

Former White House counsel Lloyd N. Cutler, arguing for the comptroller general, agreed with Davidson and Ross that the law did not violate constitutional separation of powers principles because the comptroller general is an independent officer of the United States and not controlled by Congress.

The law includes a "fallback" procedure, inserted because of uncertainty about the constitutionality of the automatic trigger.

Under that procedure, which is not being challenged in the courts in the event the automatic cutting procedures are struck down, the OMB and CBO would still calculate how much spending would have to be cut to meet deficit targets. Both the House and Senate would have to approve the cuts in a joint resolution. An impasse, such as disagreement between the House and Senate or the president's refusal to sign the resolution, would kill the process.

Appeals court Judge Antonin Scalia, a Reagan appointee and potential Supreme Court nominee, sharply questioned the law's challengers, sparring with Morrison and the union's lawyer, Lois Williams, on every aspect of their arguments.

Scalia also reopened the issue of the representatives' and the union's right to sue, an issue that appeared closed when the Justice Department conceded that the union, whose members' retirement benefits are frozen, had legal standing to sue.

Scalia asked both sides to submit briefs next week on those issues.

On the other hand, Scalia, along with U.S. District Court Senior Judge Oliver Gasch, who was appointed in 1965 by President Lyndon B. Johnson, also expressed reservations about the role of the comptroller general.

The third member of the panel, U.S. District Court Judge Norma Holloway Johnson, an appointee of President Jimmy Carter in 1980, asked only two questions toward the end of the hearing on the procedural issue.

Observers said that the trigger mechanism faces an especially uncertain future if, as expected, the Supreme Court determines its fate. The high court has not been sympathetic to congressional efforts to depart from what the justices perceive as the dictates of the constitutional separation of powers.

In a 1976 case involving the Federal Election Commission, the court struck down the appointment procedures for the commission because some members were to be appointed by the Congress to perform executive functions.

In 1983, the court struck down a legislative veto scheme where one house of Congress could affect executive branch actions and, in effect legislate outside the Constitution's strict guidelnes for enacting laws.

In addition, some justices appear willing to reject broad delegations of authority from the Congress to the president, although the last time the court struck down a law on those grounds was 50 years ago during the New Deal.