If you think President Trump’s war on Congress is leading straight to a constitutional crisis, just wait until Trump takes on the courts.

So far, the turf war between the President and Congress has been mostly about whether Congress can compel testimony from individuals who have served in the executive branch of government. The White House has instructed witnesses not to testify before the House committees conducting impeachment inquiries, based largely on a made-up, intellectually dishonest theory of “executive immunity” that has no support in law.

Some witnesses (including former U.S. ambassador to Ukraine Marie Yovanovitch and former U.S. Ambassador to NATO Kurt Volker) have defied Trump’s order not to testify. Others (including White House national security staffer John Eisenberg and White House acting chief of staff Mick Mulvaney) have complied with it.

Although one witness, former deputy national security advisor Charles Kupperman, went to court to ask a federal judge how to resolve conflicting orders from Congress and the president, the tug of war over testimony has for the most part been confined to the executive and legislative branches of government.

But the courts are rapidly becoming the new battlefield.

With apologies to legal scholars who can fill libraries with the nuances of the judiciary’s role in our system of government, let’s just say, to simplify for the sake of argument, that the Constitution and over 200 years of history have established the judiciary’s role as the neutral, non-political referee in squabbles between the other two branches of government. When the executive and legislative branches square off against each other, the courts are often called upon to step in—and if the matter under dispute is a question of law rather than politics, the courts will usually declare a winner based on law and precedent.

We are now in the early stages of judicial involvement in disputes that could have an enormous bearing on the survival of Trump’s presidency.

Some of the issues have already been teed-up in the courts, like Kupperman’s suit to resolve conflicting orders from the executive and legislative branches. That suit could have had an immediate, direct bearing on the impeachment proceedings, but now that the Intelligence Committee has withdrawn its subpoena to Kupperman—probably because his lawsuit wasn’t going to be resolved until too late for his testimony to be used in the impeachment hearings—the court will most likely dismiss the case as moot. Still, the issue of whether Trump can block witnesses from testifying is likely to get back into court one way or another.

Ironically, decisions in cases that don’t directly involve the impeachment process may wind up having more of an impact on impeachment than those that do.

Why?

Because Trump will have to decide whether or not to obey court orders. And there is peril for him in either direction.

If he obeys court orders, there will be no constitutional crisis over separation of powers, but the information that the courts have forced him to provide may become key evidence leading to his impeachment. Think tax returns and documents relating to attempts to extort Ukraine into investigating political rivals.

But what happens if Trump disobeys court orders? Who becomes the referee when the referee itself is one of the combatants?

Short answer: Congress. Because Congress alone, through its impeachment power, has the constitutional authority to hold a president accountable for breaking the law.

A look at some of the pending court cases, and a bit of informed speculation about other cases likely to come, indicates Trump’s dilemma: He’ll have to choose between complying with a court order that could yield highly damaging information about him, or defying a court order that could itself create an article of impeachment for obstructing justice and failing to faithfully execute the laws.

In the last month alone, five courts have issued rulings against Trump. None of them had anything to do with the impeachment inquiry. Rather, four of them involved the border wall and immigration green card regulations. If Trump refuses to comply with those court orders, after all appeals have been exhausted, he could be creating new grounds for his own impeachment.

The fifth case involves Trump’s attempt to block a subpoena by Manhattan prosecutors seeking eight years of Trump’s tax returns from his accounting firm, Mazars USA. In a unanimous 3-0 decision, a panel of the U.S. Court of Appeals for the Second Circuit rejected Trump’s argument of “absolute presidential immunity” and ruled in favor of the Manhattan prosecutors.

Although that decision, if not overruled by the Supreme Court, would require Mazars, not Trump himself, to turn over the documents, it could have a bearing on the impeachment process. The court’s rejection of the absolute immunity argument, although narrowly framed, could have significant negative consequences for Trump in his continuing attempts to fend off impeachment.

These cases look like just the beginning of the court battles that could put Trump to the choice of capitulating or defying court orders. What happens, for instance, if Congress or law enforcement authorities seek documents or testimony from Trump himself? Will he comply, or will he defy the courts under an argument that, as the head of a separate and equal branch of government, the courts can’t tell him what to do?

This hypothetical isn’t far-fetched. There’s precedent.

The Supreme Court’s unanimous 1974 decision in United States v. Nixon arguably ended Richard Nixon’s presidency. The Court ruled that Nixon had to turn over White House tape recordings related to the Watergate scandal. Two weeks later, he resigned.

Trump knows what happened to Nixon, and he has a much more confrontational approach to disputes. Faced with a similar decision, he could refuse to comply.

If he does, it will be up to Congress to hold him accountable through impeachment. Nobody else can. Bill Barr’s Justice Department can’t be relied upon to enforce an order against Trump. And the Supreme Court isn’t in the business of arresting or incarcerating people who defy its orders.

Of course, you can game out the hypotheticals ever further. For instance, what if Trump is impeached by the House and convicted in the Senate, but still refuses to leave the White House? What happens if Trump is defeated in 2020, but doesn’t accept the election result as legitimate? The courts would step in, but who is going to enforce their orders? Bill Barr? The military?

Such extreme scenarios don’t seem as extreme as they used to, when everybody in government operated within widely accepted norms.

But we don’t need to go to extremes to see trouble ahead. The “possible-to-likely” basket is brimming over with scenarios in which Trump might go to war with the courts, including the Supreme Court.

And then we’ll know what a constitutional crisis really looks like.