A restaurant owner who has twice gone to jail rather than serve blacks locked the doors of his small cafe tonight with a white customer inside when three black women tried to enter.

The three women, including civil rights activist Laurie Jackson of Dale City, got only as far as the enclosed porch of the Belvoir Restaurant before owner Roy E. McKoy and his wife, Patricia, came running to the door. "The lady came out the door, grabbed me by the arm and said they were closed," said Jackson.

Jackson, who had come to the restaurant Nov. 29 only to find it closed, said she will file a discrimination complaint with the Justice Department Monday against McKoy and the restaurant. The department and the FBI both are investigating complaints that McKoy, who is under a permanent federal court order directing him to serve blacks, may have defied the order.

WRC-TV (Channel 4) has reported that on Oct. 29 McKoy, who was jailed in 1967 and again in 1974 for failing to comply with the public accommodations section of the 1964 Civil Rights Act, refused to serve a television crew that included two blacks. McKoy reportedly told the crew he would serve them coffee, but it would cost "$500 a cup."

Eileen Mead, a reporter for the Potomac News of Woodbridge, was inside the restaurant today when Jackson and her two grown daughters tried to enter. Mead had entered earlier with a photographer who had left just before the three woman arrived.

"I went in, the door was open, and had a nice piece of pie and a cup of coffee," Mead said. She said after the McKoys locked out the Jackson party, Mrs. McKoy turned to her and said: "This was all set up, wasn't it, lady?"

"They do have very good apple pie," Mead said. "Homemade."

"Yeah, it's American, but not American enough," said Jackson, as she later joined reporters listening to Mead outside the restaurant.

Before the Belvoir's doors were locked and the drapes were pulled just after 5 p.m., a sign was visible inside the restaurant that read: "Our government has unconstitutionally told us whom he must serve when open for business." McKoy is known in this farming community, off I-66 about 55 miles west of Washington, as something of an eccentric for refusing to serve blacks.

As Jackson stood in the parking lot after being denied entry in the glare of television lights, a pickup truck pulled in and a woman hopped out and began cursing at the handful of reporters and Jackson.

"You all ought to be arrested," she yelled, running to the Belvoir's door. She found it locked, dashed back to the truck and drove away.

Federal and Fauquier County officials could not be reached for comment on today's incident.

When Jackson attempted to eat lunch at the restaurant eight days ago, more than 20 local law enforcement personnel were staked out across the street at the Fauquier Livestock Exchange, apparently tipped off that there might be trouble. There were no law enforcement officials at the cafe today.

Jackson said she had come to the restaurant specifically to see if she would be refused service "so I could file a complaint with the Justice Department. . . . I would say this is the most blatant example of discrimination I've seen in the area."

During a court hearing in 1967, McKoy told federal Judge Oren R. Lewis that constitutional rights did not apply to "the dark people."

His restaurant is located at a crossroads along Rte. 55, halfway between Marshall and The Plains four miles to the east, just across the street from the Fauquier Livestock Exchange.