At 11 a.m. on Sept. 13, 1975, Daniel T. Sanger, a compliance officer in Pocatello, Idaho, for the federal Occupational Safety and Health Administration, walked into the shop of a heating and plumbing contractor to check for possible violations.

His intent was to do exactly what the Occupational Safety and Health Act of 1970 authorize: enter a workplace unannounced, without a warrant, to make a routine inspection "during regular working hours and at other reasonable times, and within reasonable limits and in a reasonable manner . . ."

But the proprietor Ferrol G. (Bill) Barlow, 61, a Democratic precinct committeeman and a leader of the John Birch Society, politely blocked Sanger.

In doing so, Barlow told the official, he was doing exactly what a "higher law" - the Constitution - authorizes in the Fourth Amendment: keeping his private property "secure . . . against unreasonable searches . . ." He pointed to a copy of the amendment hanging over trays of Birch literature on the counter.

If Sanger, in conformity with the amendment, would return with a search warrant stating a probable cause for believing a violation existed, Barlow told him, then of course he could enter the nonpublic parts of the shop.

Today, the Supreme Court will hear oral argument in the legal dispute that arose from the Pocatello encounter. By early July, the justices will decide whether the warrantless inspections authorized by the 1970 law are compatible with the constitutional prohibition of unreasonable searches.

If the Supreme Court's decision were to apply only to Barlow's shop it would be unimportant. He has only 33 employees. None has complianed health or safety violations: none has filed an injury claim in the 17 years Barlow and his four sons have operated the business.

But whatever the decision, it will apply not only in Pocatello, but throughout the United States. Consequently, the stakes could be large indeed.

In 1971, the Senate Committee on Labor and Public Welfare ranked the problem of assuring safe and healthful workplaces "with any that engages the national attention today . . . 14,500 persons are killed annually as a result of industrial accidents; . . . during the past four years more. Americans have been killed where they work than in the Vietnam war. By the lowest count, 2.2 million persons are disabled on the job each year . . ."

In October a federal survey was reported to show that while at work, one of four persons is exposed to substance believed to be able to cause disease or death.

Nearly 65 million Americans work at almost 6 million jobsites. The Labor Department has only 1,300 inspectors. The department says that if they have to get a warrant before making each of the approximately 80,000 inspections they now make annually, their ability to abate occupational hazards will be seriously impaired.

Actually, the court's decision has implications ranging far beyond occupantional safety and health. If OSHA inspectors will be required to get search warrants, Solicitor General Wade H. McCree told the court in a brief filed in July, so might inspectors for a host of other federal and state agencies set up over the last 70 years.

McCree listed, among others, agencies whose missions are to assure the safety of foods, drugs, cosmetics, water, pesticides, clinical laboratories, airplanes, railroads and natural gas pipelines.

Conservatives acknowledge that they support Barlow's cause as a first step in their larger effort against federal regulation. "OSHA is merely a vehicle," Rep. George Hansen (RIdaho) says. A victory for Barlow would cripple most regulatory agencies. Hasen says.

OSHA officials agree.

In 1975, after Barlow turned away the OSHA inspector, the government persuaded a federal judge to order the businessman to let the official in. But Barlow again barred Sanger and the next day, Jan. 6, 1976, Barlow sought an injunction against warrantless OSHA inspections.

A judge promptly rejected Barlow's petition. But on appeal a year later, a panel of three judges ruled that the provisions the OSHA law authoriting warrantless inspections "are unconstitutional as being violative of the Fourth Amendnment."

In his Supreme Court brief, Solicitor General McCree said the panel's ruling "frustrates the clearly articulated intent of Congress" to promote compliance with the law with unannounced inspections that deprive employers of easy opportunities to conceal hazardous working conditions.

Arguing that the ruling "has no valid foundation in the Fourth Amendment decisions of this court," he said that there is in a worksite such as Barlow's "no significant privacy interest at stake that calls for the imposition of the warrant requirement."

Inspections during regular working hours "can hardly be said to intrude upon the employer's right of privacy in the same degree as would a search of his home, office, or person," McCree contended.

In a reply brief, Barlow's lawyer, John L. Runft of Boise, argued that, with certain exceptions, every official intrusion into privacy made without the consent of the affected party "is 'unreasonable' unless it has been authorized by a valid search warrant."

Barlow's cause has been embraced in friend-of-the-court briefs submitted by, among others, the Chamber of Commerce of the United States, the American Conservative Union, the Roger Baldwin Foundation, Inc., of the Illinois Division of the American Civil Liberties Union, and the states of Idaho and Utah.

The chamber said that reversal of the panel's ruling "would signal a broad repeal of the Fourth Amendment protections traditionally applicable to businesses."

Similarly, the conservative union, charged that "the Secretary of Labor seeks to abolish the Fourth Amendment rights of virtually every place of business in this nation." The brief went on to accuse OSHA of "arrogant and Gestapo-like actions . . ."

The ACLU unit, which claims in unrelated litigation that the Justice Department is making unconstitutional warrantless searches of residential and commercial premises, said:

"The ruling in the present (Barlow) case could affect the outcome of that litigation. Moreover, while the governmental interest sought to be advanced here - safety in the workplace - is important, we believe that important governmental interests cannot, and need not, be achieved through unconstitutional means."

The government's allies include 11 states (Kentucky, Michigan, Minnesota, New Jersey, New Mexico, North Carolina, Pennsylvania, South Carolina, Vermont, Virginia and Wyoming), the AFL-CIO, the Oil, Chemical and Atomic Workers International Union, the Sierra Club and Friends of the Earth.

In the brief for the states, Minnesota Attorney General Warren Spannaus said that if the panel's ruling is allowed to stand, "the efforts of these states to protect their workers against occuptational hazards will be severely impaired." He also wrote that "the right to privacy embodied in the Fourth Amendment was never intended to be used as a device to deny workers their right to work in a safe environment."

In a similar vein, the AFL-CIO said that under the panel's ruling it would be "impossible" for the Labor Department to effectively enforce the safety and health law, and that would "thereby endanger the health and safety of millions of American workers."

For a time, it appeared that Barlow would have at his side, the powerful array of expert legal talent commanded by the national ACLU. In June, after the organization's general counsel split 2 to 2 on whether to intervene, the ACLU's directors voted 30 to 20 to file a friend-of-the-court brief supporting Barlow.

In September, however, the board reversed itself. Associate executive director Allen Reitman said that six or seven more directors voted to stay out of the case than to participate.

ACLU legal director Bruce Ennis said there was no single overriding reason for the switch. "We decided not to intervene for tactical and substantive considerations," he said.