Congress has outlawed many forms of human behavior over the years. Unfortunately for the National Park Service, enjoying the glories of the great outdoors without clothes on is not one of them.

Thus in an era of lowered expectations, where less is more, the Park Service is being forced to grapple with what policy, if any, it should have toward nudism in the parks and beach areas where it has jurisdiction.

The reason for the current review is Jacob Riis Park Beach (across the Rockaway Inlet from Brooklyn, about a half-hour's drive from Manhattan and within an easy commute of a metropolitan area of 10 million people), where, on the easternmost part of the beach, there is a stretch of sand that has been patronized by nude sun-worshippers for 30 to 40 years.

The Park Service inherited Riis park when it formed the Gateway National Recreation Area five years ago.

For years the service has been getting complaints from nearby residents, not only about the nudity, but also that offensive sex acts occur on the beach.

There has been pressure to ban nude sunbathing on the beach, which is frequented substantially, but not exclusively, by homosexuals.

The bathers deny claims of rampant lewdness, though Park Service police say there are occasional arrests of both homosexuals and heterosexuals engaged in sex on the beach.

These cases invariably get thrown out of court, either due to the lack of a complainant or because the U.S. attoney or the District Court judge, who would have jurisdiction, feel such cases are too trivial to merit their attention.

While New York City and New York State have ordinances against disrobing and indecent exposure, this is federal land and there is also a legal ban on nudity. There is also legal question as to whether nudity in itself constitutes indecent exposure.

There is no national Park Service policy on nude bathing. Pressured by the situation here, the chief attorney for the Park Service's North Atlantic region, head-quartered in Boston, is trying to decide whether such a policy is needed.

A spokesman said such a ban also would affect other areas popular with nude bathers, including parts of Fire Island, also near New York, the Cape Canaveral seashort in Florida, Lake Meade in northern California and Cape Cod, where the Park Service last confronted the problem.

Several years ago the Park Service banned nude bathing on isolated Brush Hollow Beach on the Cape Cod National Seashore because the dune-covered area's fragile ecology was threatened. Following passage of a local ordinance, in 1975 the Park Service promulgated a federal regulation, with fines, against nude bathing.

"It's hard to explain to people that it was a management problem, and not a moral problem," said Tom Mercer, a spokesman for the Park Service's North Atlantic region.

But the ban has produced no arrests and has been hard to enforce. There have been annual "nude-ins" to defy it.

The crowds, however, have dwindled and conditions at the beach have pretty much returned to normal, eliminating the problem, according to Mercer.

Unlike Brush Hollow, Riis Park is anything but isolated or secluded.

On one hot Fourth of July weekend, the entire beach was only slightly less crowded than Coney Island.

Moreover, the nude beach - while at the eastermost end of Riis Park and away from areas frequented by families - occupies a stretch of sand in front of a home for the aged, and it abuts the middle to upper-class beach community of Niponset, which is represented in Congress by Democrat James Scheuer. The Congressman has a home in Niponset, and he, with his neighbors, doesn't like what nude bathing does to the neighborhood.

"I can sit on my deck and see all the nude bathing going on down the beach - and there is absolutely no attempt to hide it," said Scheuer. "It sends people in this community up the wall."

Rather than wait for a federal regulation "that would be litigated by the American Civil Liberties Union," Scheuer suggested that a more immediate solution would be to turn the nude and gay beach into one for senior citizens, "not only for the residents of the nursing home, but they could send the word out to senior citizens' facilities throughout the Rockaway Peninsula that this beach was reserved for them."

As for the nudists, he would send them up the beach "a bay or two."

However, "if you moved us we would be right in front of the central refreshment pavilion," pointed out one unclad bather.