JUNEAU — Attorneys for the gay couples challenging Alaska’s ban on same-sex marriage say the right to marry is fundamental and due to all individuals.

They take issue with the state saying the U.S. Supreme Court has never held that there is a fundamental constitutional right to same-sex marriage. The plaintiffs’ attorneys, in a court filing Friday, said the high court has upheld a broad definition of marriage.

They said it is unnecessary to parse out certain classes of individuals for whom marriage should apply.

In this case, “the issue is not whether there is a constitutional ‘right to same-sex marriage,’ but whether excluding people from a fundamental right that belongs to all individuals violates due process,” attorneys Allison Mendel, Heather Gardner and Caitlin Shortell say in the filing.

The state’s approach has been tried and rejected by courts in other parts of the country, they said.

The lawsuit was brought by five same-sex couples — four married outside of the state and one unmarried couple — seeking to have Alaska’s ban on gay marriage overturned as unconstitutional. Voters in 1998 approved an amendment to the state’s constitution defining marriage as between one man and one woman.

A federal judge is scheduled to hear arguments in the case on Friday.

The state, in a filing last month, said the question of whether to define marriage to include gay couples should be decided by citizens, not the courts. The state also argued that Alaska laws prohibiting recognition of same-sex marriages from other states or countries do not violate the plaintiffs’ constitutional rights.

“It is well established that a state is not required under the federal Constitution ‘to apply another state’s law in violation of its own legitimate public policy,’” attorneys for the state wrote.

The plaintiffs’ attorneys countered that the U.S. Supreme Court “has never held that a law’s democratic enactment constitutes even a rational basis for its existence.”

They also said the state’s interest in the democratic process is not advanced by excluding gay couples from marriage or by refusing to recognize same-sex marriages legally performed elsewhere.

“Discrimination must be justified by more than a desire to discriminate,” they said.