Fights over taxes usually find credit unions and the U.S. government on opposite sides. But the Justice Department has taken the unusual step of filing briefs in a tax case on the side of a credit union in its battle with its state tax authority.

The Poughkeepsie, N.Y.-based $2.7 billion Hudson Valley Federal Credit Union has taken the State of New York to court over a tax that the state applies to recording mortgages. The credit union contends that as a federally chartered credit union, it should not have to pay the state tax. The state has countered with the observation that the CU has not yet exhausted its administrative remedies to the tax and argued that the tax is not on the credit union but on the mortgage borrower.

Oral arguments before the Supreme Court of the State of New York have been scheduled for April 13.