In 1999, Judge Carolyn Gill-Jefferson upheld the law, ruling that it violates Louisiana's right to privacy but does not violate other rights protected by the state Constitution.
An appeal was filed by the Louisiana Electorate of Gays and Lesbians Inc., and nine gay or lesbian individuals, on grounds that the law "denies us the right to have sex under any circumstances," said John D. Rawls, LEGAL's attorney.
State attorneys, however, contend the law is needed to promote marriage and encourage procreation.
Arguments are scheduled Monday before the state's 4th Circuit Court of Appeal.
The case affects 63 of Louisiana's 64 parishes. A separate case in Jefferson Parish, just outside New Orleans, has been put on hold until rulings in Monday's case are final.
If LEGAL loses, the case cannot be appealed to federal court, Rawls said.
"We have not raised any federal issues in this case," he said. "It is based entirely on the broad human rights that the people of Louisiana have preserved for ourselves in the state Constitution."
Also, the U.S. Supreme Court ruled 5-4 in 1985 that the U.S. Constitution does not provide a right to privacy to gays and lesbians, he said.
Monday's appeal does not concern the right to privacy. Instead, it deals with the rest of Gill-Jefferson's findings. But the privacy issue remains under review.
In July, the state Supreme Court ruled in another case that the right of privacy did not extend to oral or anal sex in a motel room between consenting heterosexual adults.
The court reasoned that if consenting adults have such sex, both are guilty and there is no victim.
Three months later, the court ordered Gill-Jefferson to reconsider her decision that the law violates privacy rights, and the judge has scheduled arguments on that issue March 9.
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