Attorney General Jeff Sessions on Monday criticized a court order that allows for the questioning of Commerce Secretary Wilbur Ross on how a citizenship question came to be added to the 2020 census.

The court's actions, the attorney general said in a speech to the conservative Heritage Foundation, represent an improper attempt "to hold a trial over the inner-workings of a Cabinet secretary's mind."

With his remarks, Sessions waded into a simmering legal dispute that may ultimately be resolved by the Supreme Court, which solidified its conservative majority with the recent addition of Justice Brett Kavanaugh.

The conflict centers on a judge's order that Ross may be deposed by lawyers challenging whether a question on citizenship legally can be included on the census. Plaintiffs in two lawsuits, including more than a dozen states and big cities, have sued, saying the question will discourage immigrants from participating in the census.

The judge, Jesse M. Furman, has said Ross can be questioned about how the citizenship inquiry was added to the census because he was "personally and directly involved in the decision, and the unusual process leading to it, to an unusual degree." A New York-based federal appeals court backed Furman's ruling last week, but Supreme Court Justice Ruth Bader Ginsburg issued a temporary stay.