President Donald Trump’s executive order challenging birthright citizenship is set to face its first significant legal test Thursday, as a federal judge in Seattle considers a request for a temporary restraining order filed by four Democrat-led states.

This hearing represents the first salvo in what is expected to be a prolonged challenge to the president’s controversial reinterpretation of the 14th Amendment. Reagan-appointed U.S. District Judge John Coughenour is overseeing the case and could decide whether to impose a temporary restraining order by the end of the hearing Thursday, which could complicate the birthright order’s expected Feb. 19 implementation date.