WATCH: A Powerful Look At Exactly How Prop 8 Was Defeated

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Proposition 8, the 2008 California ballot initiative banning same-sex marriage in the state, sparked a five-year legal battle that is recalled in a new HBO Films documentary, “The Case Against 8.” A 90-second trailer for the film hit the Web on Friday and outlines the uphill court battle facing the lesbian, gay, bisexual and transgender community in 2008; but it also underscores the determination that led to the defeat of Proposition 8.

“By accepting a domestic partnership [instead of marriage], we also accept being second-class citizens, and that was unacceptable to us,” one of the documentary's participants says in the trailer.

The clip also highlights the involvement of conservative lawyer Ted Olson, who successfully defended George W. Bush in the 2000 U.S. Supreme Court case Bush v. Gore. Olson teamed up with David Boies -- who argued against him on the 2000 case -- to fight together for marriage equality and overturn Proposition 8. The case traveled all the way up to the U.S. Supreme Court and, in the end, Proposition 8 had been struck down as unconstitutional.

“The Case Against 8” opens in theaters June 6 and will appear on HBO June 23. It premiered in January at the Sundance Film Festival, where its directors, Ben Cotner and Ryan White, received honors for best directing. The documentary went on to win the audience award at the South By Southwest festival in March.

(Hat tip, Mashable)

CORRECTION: A previous version of this post incorrectly stated that the Supreme Court ruled Proposition 8 unconstitutional. The Supreme Court itself ruled that the private parties that appealed the case to the justices did not have standing to do so after the state of California had bowed out.