The National Guard is following orders from the U.S. Department of Defense. The DOD announced last month that same-sex couples are eligible to apply for the same identification cards and benefits that opposite-sex spouses receive as of Sept. 3, 2013.
The announcement is a response to the U.S. Supreme Court's decision in June on the constitutionality of the Defense of Marriage Act.
1st Lt. John Quin, a spokesperson for the Guard, said Missouri's National Guard has currently issued IDs and benefits for one same-sex couple.
"If you have a valid marriage certificate and you bring it to an ID center, then you can get your ID card the same as anybody else," Quin said.
Quin said this doesn't go against Missouri's gay marriage ban because the program is federally funded.
The governors of Oklahoma, Texas, Mississippi and Louisiana have directed the National Guard in their states to refuse to process requests for military benefits for same-sex couples. All four states have gay-marriage bans.
Missouri-based gay rights advocate Tracy McCreery said those states are forcing military personnel to jump through unnecessary hoops.
"I think that the states that are ignoring the federal directive are heading down a slippery slope," McCreery said. "Almost all of the benefits going to these guard units come from the federal government."
Thirty-seventy states have bans on gay marriage.