In issuing his ruling, U.S. District Judge Orlando Garcia said the same-sex marriage ban has no "rational relation to a legitimate government purpose." The judge issued a preliminary injunction following a lawsuit by two gay couples who argue the ban is unconstitutional.
Professor Aaron Bruhl with the University of Houston Law Center says the judge's ruling was based on the 14th amendment.
That amendment forbids states from depriving citizens' of the equal protection of the law.
"And in part it's important because it builds on similar rulings in other states like Utah and Kentucky and Oklahoma and Virginia. So now there's a string of victories for supporters of same-sex marriage."
But Bruhl says the ruling doesn't mean same-sex couples can start getting married in Texas.
"The judge decided he believes the Texas law limiting marriage to opposite-sex couples is unconstutional, but he's delaying the effect of his ruling to give the state of Texas the chance to appeal the case."
Legal analysts believe the issue will eventually go all the way to the U.S. Supreme Court.