PINE RIDGE, S.D. — Monique "Muffie" Mousseaux and Felipa De Leon immediately called officials at the Oglala Sioux Tribe after the U.S. Supreme Court legalized same-sex marriage in 2015 to see if they could get married.

But they learned the case didn't apply to Native American reservations and were told the OST's constitution doesn't allow for same-sex marriage. So instead of getting married through their tribe, the couple received a license in Pennington County and wed at a group ceremony at Mount Rushmore.

Four years later, the couple will soon be able to wed through their tribe after they helped change the marriage laws, which were approved with a 12-3 vote and one abstention by the OST council on July 8.

"Marriages between two people of the same sex are hereby authorized and recognized by the Oglala Sioux Tribe," an unsigned copy of the amendment reads.

"We are looking out for future generations, for protections and for equality," Mousseaux said Friday at a Rapid City coffee shop. "These foundations of laws have to be in place because we have grandkids. And that next generation coming up, we don't want them experiencing the same (gay) bashing, we don't want them to get to a point where somebody says a bad word to them because they like somebody of the same sex and they hang themselves. We don't want that."

It's "really awesome" that the ordinance passed the week before Rapid City's pride celebration last weekend and near my birthday, Mousseaux said with a laugh.

"We're doing this for all the children, everybody's grandchildren, everybody's great-grandchildren. Not just ours. But all the whole next generation," De Leon said.

They have been a couple since 2005 and live in Rapid City, but three of their five children and four of their five grandchildren live on the Pine Ridge Reservation.

Obergefell v. Hodges legalized same-sex marriage in all 50 states but not for the 573 federally recognized tribes, said Marcia Zug, a professor at the University of South Carolina School of Law who specializes in family and federal Indian law.

"Tribes have the right to make the decision themselves," she said.

As quasi-sovereign nations, tribes have control over certain rules that directly impact their tribal members even if they violate federal equal protection rules, Zug said. That principal was solidified in Santa Clara Pueblo v. Martinez, a 1978 landmark U.S. Supreme Court case that said the pueblo has the right to give tribal membership to the children of men who marry outside the tribe while preventing women who marry outside the tribe from passing on their tribal membership.

Even though tribes don't have to follow Obergefell, Zug said, "the trend is certainly moving in that direction, and I would think most in the next couple of decades will recognize same-sex marriage."

Zug said there is no geographical or historical pattern that explains why some tribes allow same-sex marriage while others don't. For example, the Navajo Nation explicitly bans same-sex marriage despite two spirit individuals being traditional Diné (Navajo) culture and other Southwest tribes allowing such marriages.

It's unclear how many tribes do allow same-sex marriage but ones that do include the Cherokee Nation, the Blackfeet Nation in Montana, and the the Northern Arapahoe and Eastern Shoshone tribes of the Wind River Reservation in Wyoming. Mousseaux and De Leon said they believe the OST is the first tribe in South Dakota to legalize same-sex marriages.

Mousseaux said she was happy to see the OST approve of same-sex marriage through its own sovereign process even if meant waiting longer.

"I am very proud of our sovereignty," she said. "I embrace that. I enjoy going through what we're going through right now. It's a great victory on all Native Americans."