13 February 2017 – Washington state’s attorney general has promised to uncover “what truly motivated” President Donald Trump’s executive order on immigration, an approach that could prompt a rare public examination of how a U.S. president makes national security decisions.

The presidential order imposed a temporary ban on travelers from seven predominantly Muslim countries, but a federal judge has barred enforcement of the order while the court considers a challenge brought by Washington state.

On Thursday, the U.S. Court of Appeals for the 9th Circuit left the judge’s ruling in place without deciding the ultimate merits of either side’s arguments. In its decision, the 9th Circuit cited a previous case establishing that “circumstantial evidence of intent, including … statements by decisionmakers, may be considered in evaluating whether a governmental action was motivated by a discriminatory purpose.”

The Trump administration has argued that the ban is necessary to prevent potential terrorists from entering the country and is not discriminatory because the text of the order does not mention any particular religion.

Washington Attorney General Bob Ferguson signaled on Sunday that he will move aggressively to obtain written documents and emails authored by administration officials that might contain evidence the order was unconstitutionally biased against Muslims or Islam. He also said he would also move to depose administration officials.

Legal scholars say this could move the court into uncharted waters.

“The idea of looking at motive has never really been applied to the president,” said John Yoo, a former Justice Department lawyer in the George W. Bush administration.

“It would represent a serious expansion of judicial oversight of what the president and the entire executive branch does,” said Yoo, now a professor at the University of California at Berkeley School of Law.