The Environmental Protection Agency got a little pat on the head last year when the President's Task Force on Private Sector Initiatives, wrapping up its year-long study of voluntarism in the federal government, cited the agency favorably for its emphasis on "voluntary compliance with environmental laws."

It appears that a redefinition of voluntarism is in order at the EPA.

According to Administrator William D. Ruckelshaus, the only voluntarism at the EPA "is if the EPA voluntarily decides not to enforce the law."

Ruckelshaus' statement puts him at rhetorical odds with both his predecessor and the White House, which has promoted voluntarism in every way, shape and form as a way of shrinking the government's size and shortening its regulatory reach.

EPA officials under former administrator Anne M. Burford repeatedly cited the importance of voluntarism, usually when they were called upon to answer criticism that the agency had gutted its enforcement division. Robert M. Perry, the agency's former general counsel, stood steadfastly beside the argument even after his March 25 resignation, telling a reporter in April that "it's ultimately voluntary compliance that is going to clean up this nation."

But critics contend that for all practical purposes EPA policy over the past two years has been voluntary compliance or no compliance at all. Budget cuts have impaired the agency's ability to inspect facilities for permit violations, they say, and the agency deliberately sheathed its most powerful weapon: the lawsuit.

While he makes it clear that he is no great fan of litigation, either, Ruckelshaus sees the debate in a slightly different light. It all has to do with the free enterprise system, and in an interview last week he explained it this way:

In the EPA's early years, he said, "I talked to some of the people in these major corporations in the country at the time and they thought the whole thing pollution control was a lot of nonsense. The secretary of commerce formed this National Industrial Pollution Control Council--Maurice Stans did--in which they fostered voluntary compliance on the part of the corporations.

"I remember going over there and talking to him, at a meeting he convened of all the chief executive officers of these major manufacturing companies, and he made a big spiel about voluntary compliance.

"And I answered and said, 'You don't believe in the free enterprise system. There's no way in the world that's going to work. Because if one of these competitors does not comply, there isn't any way the rest of them can.'

"The only way the free enterprise system can work is if there is a framework for competition that roughly provides the same kind of requirement on everybody to protect the free externalities of air and water and land . . . . So there has to be a regulatory program, and it has to be an effective national regulatory program."

NEW MATH, NEW FACES . . . Ruckelshaus sent agency officials to their abacuses this week with his answer to a reporter's question about agency personnel. In a Cable News Network interview Tuesday, Ruckleshaus said: "There are 13 presidential appointees at the national level . . . . All of them will be changed. There will be none of the original nine, plus three additional positions that we will be requesting from the Congress. They'll be different, all be different people."

Aside from the fact that nine plus three doesn't add up to 13, there are currently 10 presidentially appointed jobs at the EPA. Agency officials said Ruckelshaus wants to add an associate administrator for external affairs and one for regional affairs, but were puzzled about the third additional position he mentioned.

For keepers of box scores, the presidentially appointed positions at the EPA are administrator, deputy administrator, inspector general, general counsel and assistant administrators of air, water, pesticides, solid waste, research and administration.

Ruckelshaus is currently the only Senate-confirmed officeholder at the agency. Lee M. Thomas, a former Federal Emergency Management Agency official who has been acting deputy administrator, yesterday officially was named as Reagan's choice for assistant administrator of solid waste, the person in charge of the Superfund. All the other positions are filled by acting officials.

Ruckelshaus offered the external affairs job, which will expand the congressional liaison's job to include state and local governments, to Lee Verstandig, who held down the fort at the agency until Ruckelshaus' arrival. Verstandig declined in favor of a White House job, but agency officials say he is acting as the "talent scout" for the EPA job.

For the other new position, associate administrator for regional affairs, Ruckelshaus is expected to tap Sam Schulhof, now in the agency's office of administration. An agency spokesman said the job was another step in Ruckelshaus' effort to "further decentralize the agency, and give more authority and responsibilities to the regions."