Ten U.S. Senators have filed a “friend of the court” brief defending the constitutionality of the federal Defense of Marriage Act (DOMA), which limits federal marriage to the union of a man and a woman.

The senators contended that in striking down DOMA several months ago, a district court “failed to understand that federal law necessarily defines 'marriage' in some fashion beyond mere incorporation of state law.”

They argued that in passing DOMA Congress had the legitimate interest of avoiding “massive legal uncertainty, needless litigation and inconsistent results with regard to the availability of federal benefits.”

The June 11 brief was filed with the 9th U.S. Circuit Court of Appeals and claims that a U.S. district court was incorrect to rule against the law in February.

The senators filing the brief – Orrin G. Hatch, R-Utah, Saxby Chambliss, R-Ga., Dan Coats, R-Ind., Thad Cochran, R-Miss., Mike Crapo, R-Idaho, Charles Grassley, R-Iowa, Lindsey Graham, R-S.C., Mitch McConnell, R-Ky., Richard Shelby, R-Ala., and Roger Wicker, R-Miss. – all voted in favor of DOMA when it was passed in 1996.

They observed that the Defense of Marriage Act passed both houses of Congress with the support of more than 80%, “an overwhelming and bipartisan majority,” before being signed into law by President Bill Clinton.

The law was passed, they said, largely in response to a situation in Hawaii, in which courts appeared to be “on the verge of requiring that state to issue marriage licenses to same-sex couples.”

Congress was concerned that such state redefinition of marriage “would likely have unpredictable and inconsistent legal impacts on other states and the federal government,” the senators explained.

When the law was enacted, they noted, there were 1,049 federal statutory provisions in which marital status was a factor for benefits and privileges.

“Congress clearly had a legitimate interest in determining how these provisions would be affected by the recognition of same-sex 'marriage' in Hawaii or other states,” they said.

As a result, lawmakers passed the Defense of Marriage Act, which says that states are allowed to, but not required to, recognize “gay marriages” entered into in other states. In addition, the law defines “marriage” within federal law as only “a legal union between one man and one woman as husband and wife.”

With this legislation, Congress sought to avoid the flood of “piecemeal litigation in state or federal courts” that would likely have ensued if one or more states changed the definition of marriage, the senators said.

They also argued that the recognition of “gay marriage” had never been the “status quo” for federal purposes prior to the passage of DOMA. Rather, they said, “No state had ever recognized same-sex 'marriage,' nor had any same-sex couple ever been ‘married’ within the meaning of federal law.” Therefore, DOMA “merely clarified the existing federal law definition of marriage.”

The senators also observed that, in its opinion, the district court repeatedly asserted that the passage of DOMA was motivated by “animus,” which it purportedly found in statements by members of Congress arguing that homosexuality is immoral and marriage is limited to a man and a woman.

The court seemed to treat this alleged “animus” as creating “a presumption of unconstitutionality” and did not acknowledge that it was possible to oppose “gay marriage” without being motivated by such “animus,” the senators observed. They warned that the attempt to evaluate the constitutionality of a law based on a subjective “assessment of legislative motives” is “utterly at odds with our constitutional traditions.”

This approach “raises serious separation of powers problems” and risks creating “needless friction between the branches” of government, the senators said. It also “chills the freedom of legislative speech that is the hallmark of robust democratic debate,” they added.

“It is one thing for the district court to conclude that traditional moral views, standing alone, do not justify the enactment of DOMA,” the lawmakers said, but “it is quite another to find that legislators who hold or express such moral views somehow taint the constitutionality of the statute.”