A Vermont couple who married in April may be split up after the U.S. Citizenship and Immigration Service denied their application for a spousal green card.

Frances Herbert and Takako Ueda, a Japanese immigrant, have been together for 10 years, and Ueda has been living in the United States legally on a student visa. But that visa expired recently, and so the couple compiled 600 pages of documentation to apply for a green card on the basis that Ueda is married to an American citizen.

But on Dec. 1, they received a letter from the Citizenship and Immigration Service informing them that their application had been denied and instructing Ueda to return to Japan within 30 days.

It's despicable, Herbert told The Washington Post. We had 600 pages of proof [of our marriage], and 599 of them were completely ignored. One line on one page is what they paid attention to.

That was the line that said Herbert and Ueda were both women.

Their marriage is legal in Vermont, which began allowing civil unions in 2000 and same-sex marriage in 2009. But the Defense of Marriage Act forbids the recognition of same-sex marriages at the federal level, and the letter Ueda received said, Your spouse is not a person of the opposite sex. Therefore, under the DOMA, your petition must be denied.

Now the couple and their lawyer, Tom Plummer of the legal aid group Immigration Equality, are asking that Ueda's deportation to be stayed until a federal court can rule on whether DOMA is constitutional.

Many people have questioned the constitutionality of the law -- which was signed in 1996 by President Bill Clinton and defines marriage as only a legal union between one man and one woman as husband and wife for federal purposes, but allows the recognition of same-sex marriages by individual states -- under the due process and equal protection clauses of the 14th Amendment, and the Obama administration announced in February that it would no longer defend DOMA against legal challenges.

Several cases challenging DOMA are making their way through the federal court system, but until rulings are handed down, it remains in effect.

Ueda probably will not be deported if she fails to leave the country by Dec. 31, because immigration officials are overwhelmed and thus tend to focus on people who have criminal records or otherwise pose a threat to the country. But she would become an illegal immigrant, which neither she nor Herbert wants.

Takako has been here lawfully, Herbert told The Brattleboro Reformer, a local newspaper. We haven't done anything that is questionable under the law. She's been a student. We aren't a threat to this country, and neither are thousands of other couples. We just want to be respected and live our lives and carry on without the threat of Takako being shipped back to Japan.