The chief justice is right to be concerned about Trump’s antijudicial language, which points to the most serious danger that may lie ahead: the administration’s overt defiance of a judicial order. This would amount to denying that the courts have the final authority in the interpretation and application of federal law.

If such an overt defiance were to occur, the courts have some measures available to them, but they may in practice be of limited utility against a determined executive branch. In the event of a judicial finding that an official who knowingly violated a court order was guilty of criminal contempt of court, the official might be pardoned by the president. A civil contempt finding could impose monetary fines on an official, and in theory a court could order the official detained until payment is made. But the arrest would ordinarily be made by the US Marshals, part of the executive branch and housed in the Department of Justice, and they might be directed by Trump not to cooperate with the judiciary. The courts could potentially direct some other person to enforce their orders against an employee of the executive branch. But if Trump were to direct other executive branch personnel to protect the official held in civil contempt, it seems unlikely that a third party could coerce the official into court-ordered custody.

A situation like this, in which a court ordered the Trump administration to act and it flatly refused, would almost certainly qualify as a genuine constitutional crisis. The term “constitutional crisis” is descriptive, not legal. No official definition appears in the Constitution or federal law or Supreme Court precedent. I define a constitutional crisis as a situation in which the Constitution does not provide a clear, definitive answer to a basic problem of governance and the political figures in conflict are ready to press their competing courses of action to the limit.2

The classic American example was Richard Nixon’s refusal to honor parts of the subpoenas served on him for the Watergate tapes.

In such situations, no one can say for certain what the outcome will be. A compromise may resolve the crisis, or one of the two sides may prevail. Congress impeached Nixon, charging him with ignoring the order, among other high crimes and misdemeanors. He turned over some parts of the tapes but not others and subsequently resigned. That outcome seems vanishingly unlikely in any conflict between Trump and the courts.

If Trump were to prevail in a confrontation with the courts, it would be devastating to the rule of law. Perhaps some members of the public would protest. But it is hard to imagine that affecting Trump’s course of action. People in other countries might express shock and condemnation, but again, Trump seems unlikely to care. One would think, indeed hope, that the markets would respond with serious concern. The rule of law protects not only persons but property. Yet it is also conceivable that the markets might think Trump’s (still hypothetical) disobedience would be restricted to noneconomic matters and remain unmoved. After all, markets function even in many autocratic countries. And partial rule of law, restricted to economic matters, is not unknown in the world, historically or today.

If the courts were to prevail, and Trump bowed to their pressure with respect to a given order but remained in office, he might pay very little price. His opponents already see him as a potential dictator. His supporters might not care about his disobedience, especially if he backed down. Trump may have little to lose in experimenting with disobeying judicial orders, even if he precipitates a crisis. As Alexander Hamilton famously observed, the judiciary “has no influence over either the sword or the purse…and must ultimately depend upon the aid of the executive arm even for the efficacy of its judgments.” That means, ultimately, that the Supreme Court needs the president to believe, or at least to act as though he believes, that violating its interpretation of the law would break the constitutional order. Like it or not, the legitimacy of the Supreme Court is now the most important bulwark of our delicate constitutional democracy.