A federal judge ruled yesterday that the Loudoun Golf and Country Club is not exempt from antibias provisions of the 1964 Civil Rights Act, clearing the way for a trial on a $125,000 lawsuit alleging the club practices racial discrimination.

U.S. District Judge Richard L. Williams rejected arguments by lawyers for the club that it is a private facility and that the suit's claims are barred by Virginia's statute of limitations.

The Civil Rights Act bars racial discrimination by public facilities, but includes a clause exempting private clubs in accord with First Amendment guarantees of freedom of association.

Norman Green, a white club member, and his black guest, Arthur Brown, both of Reston, filed the complaint in June in U.S. District Court in Alexandria, a year after Brown allegedly was asked to leave the golf course by the club's golf pro.

The pro, Jimmy Bogle, told Brown to leave the club because he was black, according to court papers filed by the plaintiffs. Bogle has denied the allegation.

Attorney Jaclyn Leonhard, representing Brown and Green, argued in court yesterday that membership policies of the 56-year-old club, located in Purcellville, were not sufficiently selective to qualify the facility as private.

Leonhard said all 120 applicants who asked to join the club since March 1982 have become members.

"The numbers showed they were not being picky about who they were letting in," Leonhard told Williams.

Leonhard said outside the courtroom that an adverse ruling by Williams yesterday would have dealt a severe blow to the complaint.

Pamela S. Horowitz, a lawyer for the club, contended that the organization is private because applicants must have two sponsors and conform to club procedures before being admitted to membership. "You have a certain amount of selectivity before applications are submitted," Horowitz said.

Leonhard argued, however, that "truly private clubs" are operated and owned by their members, while only 60 shareholders of the Loudoun club's 450 members elect a board of directors.

The executive director of the Lawyers' Committee for Civil Rights Under Law, William L. Robinson, said yesterday in an interview that membership selection, access to a facility and club operations are common criteria used in determining whether an organization is private.

Green, 51, a real estate agent, joined the club in 1980 as one of 200 new, discounted-fee members. "Mr. Green became a member because he knew two members," said Leonhard, arguing that current membership procedures differ sharply from those in 1927 when applicants were not invited to join unless they were related or associated with members.

"The character of the club has changed," Horowitz said, "while suburbia has crept out to the country."

Brown and Green also have asked the court to order the club to stop its alleged discriminatory practices.

No trial date has been set.