The court clerk in Marion County, home to Indianapolis, began issuing marriage licenses to same-sex couple about an hour after U.S. District Judge Richard Young ruled that the state law violates the U.S. Constitution's equal-protection clause.
"Same-sex couples, who would otherwise qualify to marry in Indiana, have the right to marry in Indiana," he wrote. "These couples, when gender and sexual orientation are taken away, are in all respects like the family down the street. The Constitution demands that we treat them as such."
The Indiana attorney general's office said it would appeal the ruling but declined further comment.
The ruling involves lawsuits filed by several gay couples, who along with the state had asked for a summary judgment in the case. Young's ruling was mixed but generally sided with the couples and prevents the state from enforcing the ban.
"Indiana now joins the momentum for nationwide marriage equality and Hoosiers can now proclaim they are on the right side of history," Lambda Legal, the national gay rights group that represented five of the couples, said in a statement.
The decision came the same day the 10th U.S. Circuit Court of Appeals upheld a lower court ruling overturning Utah's gay marriage ban, marking the first time a federal appeals court has ruled that states must allow gay marriage. That ruling puts the issue a step closer to the U.S. Supreme Court.
A movement to ban gay marriage in the Indiana Constitution faltered during this legislative session when lawmakers removed language about civil unions from the proposed amendment. That means the soonest the issue could appear on a ballot would be 2016.