Multiple states on Thursday announced they are suing the Trump administration over its policy of separating families who illegally cross the U.S.-Mexico border, saying the president's executive order does not resolve the issue.

Washington Attorney General Bob Ferguson (D) said he will lead a coalition of states in the lawsuit. Democratic attorneys general from Maryland and Massachusetts are among those who have signed on.

“This is a rogue, cruel and unconstitutional policy," Ferguson said in a statement. "We’re going to put a stop to it."

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The lawsuit, expected to be filed Thursday in U.S. District Court in Washington state, alleges that the Trump administration violated the due process rights of parents and children who were separated. Ferguson called the policy “arbitrary and capricious" and "irrationally discriminatory" because it targets individuals near the southern U.S. border.

Thousands of migrant children have been separated from their parents as a result of the administration’s “zero tolerance” policy that compelled law enforcement to criminally prosecute illegal border crossers, which in turn led to children being taken from their parents upon arrest.

President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE signed an executive order Wednesday to halt the separation of families at the border after saying for days that only Congress could address the issue. However, the order does not specify how and when children would be reunited with their family members.

As a result, the lawsuit will ask the court to order the Trump administration to reunite families affected by the executive order.

New York has announced a separate lawsuit against the Trump administration over its family separation practices. Attorney General Barbara Underwood tweeted Thursday that the state "will announce next steps in the coming days," though it's unclear if she will join Ferguson's lawsuit.