One of the most conservative judges in the country just handed down an opinion saying that the Trump administration acted illegally when it permitted the state of Arkansas to strip health coverage from thousands of Medicaid beneficiaries.

Judge David Sentelle’s opinion in Gresham v. Azar, on behalf of himself and two of his colleagues on the United States Court of Appeals for the District of Columbia Circuit, is significant in its own right. But it is also significant because it suggests that the Trump administration will have a tough time defending its conduct if this case is heard by the Supreme Court. Sentelle is one of archconservative Justice Neil Gorsuch’s early mentors — Gorsuch clerked for Sentelle shortly after he graduated from law school. And Sentelle’s views are well to the right of the median Supreme Court justice.

Sentelle is a protégé of the late Sen. Jesse Helms (R-NC), a segregationist who thought so highly of Sentelle that he once said that he “would do whatever I could to make sure that this young man’s integrity and talent, principles and courage, would be used by this country.” As a judge, Sentelle joined an opinion complaining that the Supreme Court abandoned doctrines it once used to strike down labor protections such as the minimum wage.

The case involves an effort by the state of Arkansas to impose a work requirement on many Medicaid beneficiaries. Arkansas could not implement this policy on its own; it had to obtain permission from the federal government. And the Trump administration gave Arkansas the permission it sought.

The consequence of that decision, Sentelle writes, was that “more than 18,000 people (about 25 percent of those subject to the work requirement) lost coverage as a result of the project in just five months.”

The Trump administration cannot push Medicaid policies that run counter to Congress’s stated objectives

Gresham turns on the scope of the federal government’s power to approve experimental state programs that depart from the way Medicaid normally operates. The law permits the Department of Health and Human Services to approve “any experimental, pilot, or demonstration project which, in the judgment of the Secretary, is likely to assist in promoting the objectives” of Medicaid.

But those objectives were also defined by Congress. Among other things, the Medicaid statute states that the purpose of the program is to “to furnish ... medical assistance on behalf of families with dependent children and of aged, blind, or disabled individuals, whose income and resources are insufficient to meet the costs of necessary medical services.”

The thrust of Sentelle’s opinion in Gresham is that the Trump administration ignored this purpose, and tried to replace it with different objectives.

Trump officials approved Arkansas’s work requirements because it thought that these requirements would “address behavioral and social factors that influence health outcomes” and encourage Medicaid beneficiaries to find work — something the Trump administration believes is “correlated with improved health and wellness.”

But even if the Trump administration is right that a work requirement will, in the long run, lead to better health outcomes, the law does not permit them to substitute their own opinions about how to improve poor people’s health. As Sentelle writes, “the Supreme Court and this court have consistently reminded agencies that they are ‘bound, not only by the ultimate purposes Congress has selected, but by the means it has deemed appropriate, and prescribed, for the pursuit of those purposes.’”

In this case, Congress decided that “the principal objective of Medicaid is providing health care coverage,” not to encourage people to find jobs by making their health coverage contingent upon securing work.

Under Sentelle’s opinion, the Trump administration could conceivably revive Arkansas’s work requirement if it provided an adequate explanation of how that requirement would foster Medicaid’s goal of expanding coverage to poor people. But given the fact that the requirement caused thousands of people to lose health coverage, it seems unlikely that the administration will clear that hurdle.