MISSOULA (AP) — Same-sex marriage was Saturday's rallying cry as at least 200 people gathered for this year's gay and lesbian Montana Pride Celebration.

‘‘Can a constitution stand, I ask you, that calls for queer apartheid?'' asked University of Montana professor Casey Charles. He was one of several speakers to take issue with a proposed state constitutional amendment that would define marriage as being between a man and a woman.

State Rep. Christine Kaufmann, D-Helena, drew a comparison between fighting for same-sex marriage and the battle for recognition of racially mixed marriages. Kaufmann said California acknowledged marriage between blacks and whites in 1948, 19 years before the Supreme Court found that marriage is a civil right.

‘‘Constitutions are meant to protect personal rights, not take them away,'' said Kaufmann, co-director of the Montana Human Rights Network.

Other advocacy was more lighthearted.

In the Rainbow Parade, a couple in wedding attire waved from a red convertible that bore the banner, ‘‘Just Illegally Married.'' Other signs read, ‘‘Love the Sinner and Her Girlfriend'' and ‘‘Straight But Not Narrow.''

Dave Jordan, a married ski instructor from Butte, arrived at the event dressed as a woman to show his solidarity.

‘‘It's a celebration and a show of unity,'' he said. ‘‘We like to show our diversity.''

Jordan and his wife, Robin, said the proposed constitutional amendment is a threat to all Montanans.

‘‘It's important for everybody to support civil rights because if we pass the constitutional amendment saying gay people are in a separate class, they can't get married, it's a step backward,'' said Robin Jordan. ‘‘That's not what our country's about.''

The three-day gathering offers workshops and social events. Along with several advocacy groups, four churches have opened their buildings to weekend visitors.