A US federal judge has temporarily halted President Donald Trump’s signature wall project, by issuing a temporary injunction against using Defence Department funds to pay for the border wall with Mexico.

Trump who during his campaign for presidency had said he would make Mexico pay for the wall, later change his stance in office and requested money for it.

Congress, including Republican members, refused to accede to his request. Trump, in reaction, triggered 35 days of a government shutdown, the longest in history, to blackmail congressmen.

When this did not work, he declared an emergency in a bid to bypass Congress to obtain money for the wall construction. The emergency enabled him to divert a part of the defence budget for the wall.

About 20 states, including Democratic strongholds New York and California, along with the American Civil Liberties Union (ACLU), environmental groups and border communities challenged him on the emergency declaration, saying it violates the constitution.

Trump administration officials “are enjoined from taking any action to construct a border barrier in the areas defendants have identified as Yuma Sector Project 1 and El Paso Sector Project 1 using funds reprogrammed by DoD,” Judge Haywood Gilliam ordered, referring to the Department of Defence.

Acting Defense Secretary Patrick Shanahan approved the diversion of funds from the department’s counter-narcotics budget for ultimate use in the construction of barriers in those areas — a move that was in turn funded by the diversion of $1 billion from army personnel funds, according to Gilliam’s order.

The judge granted the preliminary injunction because plaintiffs are likely to show that Trump administration officials “exceeded their statutory authority and that irreparable harm will result from those actions.”

“Congress’s ‘absolute’ control over federal expenditures — even when that control may frustrate the desires of the Executive Branch regarding initiatives it views as important — is not a bug in our constitutional system,” Gilliam wrote.

“It is a feature of that system, and an essential one,” the judge said in a wire report.

The case — which was brought by plaintiffs including the Sierra Club environmental group — names Trump as well as Shanahan, acting Secretary of Homeland Security Kevin McAleenan and Treasury Secretary Steven Mnuchin as defendants.

“We applaud the court’s decision to protect our Constitution, communities, and the environment today,” Sierra Club managing attorney Gloria Smith said in a statement.

“We’ve seen the damage that the ever-expanding border wall has inflicted on communities and the environment for decades. Walls divide neighbourhoods, worsen dangerous flooding, destroy lands and wildlife, and waste resources that should instead be used on the infrastructure these communities truly need,” Smith said.

“Yet again, the American people have had to look to our courts for a check on President Trump’s unlawful power grabs.”