A fundamentalist Baptist preacher who claims interracial relationships are forbidden by the Bible had a constitutional right to expel a 14-year-old white girl from his private school for allegedly dating a black classmate, a federal judge in Alexandria ruled yesterday.

U.S. District Court Judge Oren R. Lewis, in an 11-page decision, said the government may not interfere with the preacher's First Amendment right to forbid interracial dating at the school as a matter of religious principle.

Aleck Lee Bledsoe, the 37-year-old principal of the Marumsco Christian School in Woodbridge, was sued by the American Civil Liberties Union on behalf of the girl and her parents. ACLU lawyer Victor Glasberg said yesterday he would appeal Lewis' decision to the 4th U.S. Circuit Court of Appeals in Richmond.

The decision means, "You can practice racism as long as you do it in the name of the Lord," Glasberg said. "I'm not surprised enough to be angry."

Raymond Fiedler, the girl's father, said yesterday, "We expected this. But I've come this far and put my family through enough pain and torture. I'll go as far as I can go." Fiedler said if the Supreme Court rules against him, "There's still a higher judge. And I think He will agree with me."

Fiedler said his daughter, Melissa, was "very blue" last night about the decision. "I'm sure she's crying a lot," he said.

Bledsoe's attorney, Theodore H. Amshoff Jr., a Louisville, Ky., specialist in religious cases, called Lewis' finding "a victory for the First Amendment rights of the church . . . even if those religious beliefs are not popular or accepted by the public."

Amshoff, who had quoted the Bible in his courtroom defense of Beldsoe, added, "The ultimate authority for law is the Constitution."

The case, seen as a constitutional clash between religious freedom and civil rights that could reach the Supreme Court, was a difficult one for the 77-year-old judge, a source close to him said. Lewis, surrounded by law books, labored for more than a week over the emotional issue, the source said.

"Although the defendants' religious convictions regarding interracial romantic relationships do not comport with public policy, nor meet with the majority acceptance," Lewis wrote yesterday, "the government may not penalize nor discriminate against individuals or groups because they hold religious views abhorrent to the authorities."

Although neither side disputed the facts of the case, they had sharply differing interpretations of Bledsoe's action.

Melissa Fiedler, 14, was expelled from the 165-pupil school on Jan. 8 after Bledsoe told he not to speak with Rufus Bostic III, a black classmate. Bledsoe testified that he "was under the impression it was a romantic relationship."

The minister, short and stocky with a crew cut, told the court that although his school promoted racial harmony, it opposed interracial "dating" on religious grounds.

Melissa and her father, Raymond Fiedler, both testified that Rufus Bostic was not the girl's "boyfriend."

After Melissa was expelled, her father contacted a local civil rights group. When Bledsoe was informed that Fiedler intended to file a lawsuit against the school, the preacher also expelled Melissa's sister, 11-year-old Charlotte.

"Of course everyone has the right to have a romantic relationship with whom they please," Lewis wrote, "but it does not follow that they have a constitutional and/or statutory right to remain in a private sectarian school whose conscientious religious beliefs prohibit interracial romancing."

The court heard conflicting testimony on whether the ban on interracial dating was the church's policy or Bledsoe's personal belief.

The black classmate's father, Rufus Bostic Jr., who had served as a deacon for Bledsoe's Marumsco Christian Church, testified that he had never heard the preacher speak on the subject of interracial dating or marriage.

Melissa Fiedler testified that the only time she had ever heard Bledsoe speak on the subject was when he told her and other students that interracial couples would be "exterminated" if a foreign power ever took over America.

Raymond Fiedler, a $20,000 a year technician for Washington Gas Light Co. said in court that he couldn't believe such "poppycock" was being taught in the school. $5Bledsoe said from the witness stand that the Bible contained several references to God's opposition to interracial dating.

Judge Lewis at one point threatened to clear the courtroom after laughter broke out among spectators during the minister's testimony.

Bledsoe and the Marumsco Christian School filed for bankruptcy last week on the opening day of the trial, although Bledsoe said he expects the school to open as scheduled this fall.

The Fiedlers had accused the school of violating Melissa Fiedler's civil rights and had asked that both girls be reinstated to the school. They also sought $70,000 in damages.