Strict scrutiny applies. Today, for the first time, a federal court of appeals has held that "A state may not deny the issuance of a marriage license to two persons, or refuse to recognize their marriage, based solely upon the sex of the persons in the marriage union."
The case is Kitchen v. Herbert (10th Circuit 06/25/2014), decided on a 2-1 vote.
Applying "strict scrutiny" because the case involves the "fundamental right" to marry, the majority rejected every justification advanced by the State of Utah.
The dissent would apply "rational basis" rather than strict scrutiny, and hold that Utah's ban on same-sex marriage is "rationally related to (1) responsible procreation, (2) effective parenting, and (3) the desire to proceed cautiously in this evolving area."
The court put its decision on hold pending a petition to the US Supreme Court for a writ of certiorari.