California Attorney General Xavier Becerra plans to announce a lawsuit on behalf of the state that will challenge US President Donald Trump’s proposal to build a wall at the US-Mexico border.

Becerra, who has called the project “medieval”, is scheduled to travel to Border Field State Park near San Diego to announce that a lawsuit is being filed in federal court over construction of border wall projects in San Diego and Imperial counties, the Los Angeles Times reported on Wednesday.

The lawsuit, which includes the California Coastal Commission as a plaintiff, states its purpose is “to protect the State of California’s residents, natural resources, economic interests, procedural rights, and sovereignty from violations of the United States Constitution” and federal law.

It adds that the wall would have a chilling effect on tourism to the US from Mexico.

The state’s lawsuit alleges that the Trump administration has failed to comply with federal and state environmental laws and relied on federal statutes that don’t authorize the proposed projects.

The brief alleges the federal government violated the US constitution’s separation-of-powers doctrine “by vesting in the Executive Branch the power to waive state and local laws, including state criminal law”.

The lawsuit also says the Department of Homeland Security decided to build the walls without complying with the Clean Water Act and the National Environmental Policy Act.

As a result, the lawsuit alleges, the federal government lacks proper environmental analysis of the impact of 400-foot prototypes of the wall currently planned, as well as the 2,000-mile-long final wall.

The Democratic attorney general has been critical of the wall for months, including in April during an appearance on ABC’s “This Week.”

“I’m still trying to figure out who believes that a medieval situation to fix our broken immigration system is what we need,” Becerra said.

He also accused Trump at the time of reneging on his promise to have Mexico pay for the wall.

“I think American taxpayers probably are very much aligned with Mexico. None of them, whether it’s Mexico or our taxpayers, wants to pay for a medieval wall,” he said.

This is the latest of more than two dozen lawsuits and legal briefs filed against the Trump administration by Becerra, who was appointed attorney general in January and is running for election to the post next year.

He previously sued to challenge Trump’s plans to end a program that protects young immigrants from deportation, ban immigration from some countries and roll back environmental laws.

Becerra’s lawsuit is the latest attempt by California Democrats to fight the wall proposal. A bill that would have banned state government contracts for any company that helps build the wall passed the state Senate, but stalled recently in an Assembly committee.