Four residents of this city have won a rehearing of their suit charging real estate brokers with illegal price fixing, but their attorney says their fight is far from ended.

The U.S. Supreme Court ruled Tuesday that brokers can be sued under federal antitrust laws when they agree among themselves to charge identical commissions.

Such transactions involve interstate commerce, the court ruled, because buying and selling real estate here involves a great deal of out-of-state mortgage money and title insurance.

The plaintiffs -- two lawyers, a former economics professor at the University of New Orleans and an economics professor there -- had contended that the nearly uniform 6 percent commission on home sales of up to $100,000 violated federal law, but they lost in District Court and Appeals Court.

In a unanimous decision Tuesday, they won a rehearing, which means that the case will return to federal District Court here.

However, the proving of "parallel behavior" -- the 6 percent fee -- is not enough to win the plaintiffs' case, said Richard Binet, their lawyer.

Binet said he also will have to show that area Realtors acted consciously to fix commissions. Binet said that he can back this assertion with evidence. "We didn't start this case by the seat of our pants," he said.

The suit seeks $180 million in damages and is aimed at real estate trade associations in Orleans and Jefferson parishes (counties), six area firms and every agent who has done business in the area since the case was filed in October 1975.

Chief Justice Warren E. Burger wrote that persons filing such suits need prove only that the brokers' activity has a substantial effect on interstate commerce.

They do not have to prove that the alleged conspiracy had an impact on interstate markets. The plaintiffs had charged that the commission does have such an effect.

Besides giving a new trial to the New Orleans matter, this decision may open the way to a case involving three Realtors and six real estate firms in Maryland who were convicted in 1977 on price-fixing charges.

Their appeal has been delayed pending the outcome of the New Orleans case.