Plaintiffs in the case that successfully overturned California's ban on gay marriage speak out in a new trailer for the upcoming HBO documentary The Case Against 8.

The Case Against 8 takes a behind-the-scenes look at the people and politics that helped shape the case that brought down Proposition 8, California's 2008 voter-approved constitutional amendment limiting marriage to heterosexual couples.

Plaintiff couples Kristin Perry and Sandy Stier and Paul Katami and Jeff Zarillo discuss the case in a new trailer released Tuesday.

“After Proposition 8 passed, we realized that our rights were at stake,” Katami says in the 60-second video.

“The fact is that marriage means something in our society,” Stier says. “And we wanted access, and we wanted to feel like we were equally a part of society.”

“When you go through something that challenging together, there is a bond that is hard to break,” Perry adds. (The video is embedded on this page. Visit our video library for more videos.)

The film opens in New York and Los Angeles on June 6, the first anniversary of the landmark Supreme Court ruling in the case. The documentary will expand to selected cities June 13.

The Case Against 8, which won the Directing Prize for U.S. Documentary at the 2014 Sundance Film Festival, premiers Monday, June 23 on HBO.