The Democratic National Committee on Thursday filed a lawsuit alleging that Donald Trump’s administration secretly changed a postcard used by U.S. citizens overseas in a way that makes it harder to register to vote.

The lawsuit contends that the Department of Defense made the change by declaring an emergency, which allowed it to eliminate a specific box on the form. That box is typically checked by potential voters who acknowledge they are U.S. citizens but who have never lived in the United States.

They are usually the children of U.S. citizens, and 38 states allow them to cast ballots provided they have close family connections. Since 2013, the box has appeared on postcards sent to overseas voters.