Montana's ban on same-sex marriage was struck down Wednesday afternoon by a federal judge who called the ban unconstitutional.
U.S. District Judge Brian Morris did not stay his injunction, which means state officials could begin issuing marriage licenses to same-sex couples immediately.
In 2004, Montana voters passed an amendment to the state Constitution defining marriage as between one man and one woman.
In his ruling, Morris said that amendment violated the Equal Protection Clause in the 14th Amendment of the U.S. Constitution and barred Montana from enforcing it.
Same-sex couples in Montana come from all walks of life, the ruling said. Quoting a 2009 case, it went on to say that research indicates that children raised by same-sex couples "fare just as well as their peers physically, psychologically, emotionally, cognitively and socially."
"No family wants to deprive its precious children of the chance to marry the loves of their lives," the ruling added. "Montana no longer can deprive plaintiffs and other same-sex couples of the chance to marry their loves."
Montana Atty. Gen. Tim Fox plans to appeal the decision, saying in a statement Wednesday that it's his duty to do so "until such time as there is no further review or no appeal can be made in a court of law."
Last month, the U.S. 9th Circuit Court of Appeals, whose jurisdiction includes Montana, found bans on same-sex marriage to be unconstitutional. Within weeks, Montana was left as the only state in the western U.S. where marriage licenses were not being issued to same-sex couples.
Wednesday's ruling came in a case filed in May by four same-sex couples, backed by the American Civil Liberties Union. Three of those couples were married in other states and sought to have those marriages recognized in Montana. The fourth was seeking to wed in Montana.
"Montana is no longer left in the cold. It joins the ranks of states where all committed, loving couples can marry," Elizabeth Gill, staff attorney with the ACLU Lesbian Gay Bisexual and Transgender Project, said in a statement.
Currently, more than 30 states and the District of Columbia allow same-sex couples to marry.