In at least one field of constitutional law, separation of powers, all those politicians who advocate "strict construction" of the Constitution by the courts are now getting what they asked for--and the impact is being felt throughout the system.

It is being felt in the debates over the presence of U.S. Marines in Lebanon, in the controversy over the Interior Department's coal-leasing program, and in the the debate over the Federal Trade Commission's reauthorization.

It is being felt in the House and Senate Judiciary committees, still struggling to reconstruct the nation's bankruptcy courts. Finally, it is about to be confronted by hundreds of U.S. magistrates, whose authority is threatened by a "separation of powers" ruling last month by the 9th U.S. Circuit Court of Appeals.

All these controversies have one thing in common: they result from, or are complicated by, court rulings designed to insulate one branch of government from another. They are the product of an uncompromising interpretation of the separation-of-powers provisions of the Constitution, which may turn out to be a hallmark of the current Supreme Court.

It surfaced in the court's 1976 decision in Buckley v. Valeo, which held that the Federal Election Commission was unconstitutional because congressional leaders were allowed to appoint its members. The trend continued in 1980, when the court (in U.S. v. Will) ruled that Congress acted unconstitutionally when it denied cost-of-living increases to federal judges.

Then, in 1982, the justices (in Northern Pipeline Co. v. Marathon Pipeline Co.) struck down Congress' attempt to streamline the nation's bankruptcy courts, saying it gave bankruptcy judges the powers of regular federal judges but without any of their protections, such as life tenure.

Last term, in the most publicized of the rulings (INS v. Chadha), the court struck down the legislative veto, which allowed one or both chambers to block executive branch actions. The War Powers Act, which allows Congress to block the deployment of U.S. troops, was one victim. Because of it, the ability of Congress to shape the role of the Marines in Lebanon is even more uncertain than it was before.

In the coal-leasing controversy, Interior Secretary James G. Watt offered coal tracts in defiance of a congressional committee. He argued that the ruling wiped out Congress' authority over the program.

The same ruling deprived Congress of the power to veto FTC regulations. Debate over how to regain authority is now complicating the reauthorization of that agency.

The rulings reflect an extraordinarily strict reading of the Constitution. It says Congress must present legislation to the president and the justices said that means all legislation, even when disguised as something else.

Article III of the Constitution says that judges "shall hold their Offices during good Behaviour" and shall receive compensation "which shall not be diminished during their Continuance in Office." In the bankruptcy case, the court said that means all federal judges, including anyone who looks and acts like a federal judge.

The lower courts are taking their cue. Relying on the bankruptcy ruling, the 9th Circuit ruled on Aug. 5 that Congress acted unconstitutionally in 1979 when it broadened the power of U.S. magistrates.

Magistrates (259 full-time, 230 part-time) supplement the work of federal judges in every district in the country, presiding over misdemeanor trials and preliminary proceedings in felony trials, setting bail, issuing warrants and making recommendations on other matters.

Until 1979, however, magistrates had no statutory authority to render final judgments; they could only make recommendations to U.S. District Court judges. That year, as a way of relieving overworked judges, Congress moved to let magistrates enter final judgments in civil cases on their own as long as all parties to a case consented.

In making final judgments, a 9th Circuit panel said in Pacemaker Diagnostic Clinic of America Inc. v. Instromedix Inc., the magistrates exercise the authority of federal judges. But unlike the judges, they are appointed for eight-year, renewable terms. And while the salaries of judges may not be reduced, the magistrates' salaries can be cut. In fact, a magistrate's job may be eliminated.

"Magistrates might be wary of delivering unpopular opinions if the results of such decisions were curtailment of their authority, future reference in only the most mundane or onerous cases or failure to be reappointed," the panel said.

Nationally, magistrates exercised their expanded authority in 3,127 cases in the year that ended June 30, according to statistics provided by Duane R. Lee, chief of the Division of Magistrates of the Administrative Office of the Courts.

If the ruling, which is expected to be appealed, is upheld by the Supreme Court, that's 3,127 more cases for district judges to handle each year. While this won't create any new crisis, it could add to an existing one: the crushing workload of all federal judges.