Democrats sued Wednesday to block Donald Trump’s latest executive order restricting mail voting, arguing that the U.S. Constitution empowers states and Congress, not the president, to determine who is eligible to vote by mail.

The lawsuit marks the second round of battles over the president’s power to control elections. Trump’s opponents handily won the first round last year, blocking his initial executive order intended to reshape election procedures by convincing multiple federal judges that it was likely unconstitutional.

Trump on Tuesday announced that his administration would compile lists of who is eligible to vote in states and that the U.S. Postal Service would only mail ballots to those who met that criteria. Critics note that there’s little time to comb through voter rolls before ballots start going out for this fall’s elections, in some places as soon as September, and question whether the administration’s list would be reliable.