After The Supreme Court of The United States declared the Defense of Marriage Act (DOMA) unconstitutional, the Internal Revenue Service announced that it would allow same-sex couples to file as a married couple if they were married in a state that allows it, even if they live in a state that doesn't.
North Dakota now has a tax form for married same-sex couples, and it's precisely because the state doesn't recognize such marriages. Thirty-four other states ban same-sex marriages. Some, like North Dakota, have created work forms as a way to deal with same-sex filings. Wisconsin, for example, has a Schedule S that appears to be similar to ND-1S. Some advocates for same-sex marriage nationwide say the discrepancy between federal and state tax filings could be grounds for lawsuits based on the equal protection clause of the U.S. Constitution.
TwinCities.com has the complete story.