In personal style as in haberdashery, U.S. Attorney-General William Barr is conservative in an old-school way: quiet, dutiful, not given to showy demonstrations of emotion except the occasional flash of anger at Democrats and reporters he considers insolent for their probing questions. He walks with the air of a schoolmaster, which his father was, and with the discipline of that often-cheerless trade.

But this week Mr. Barr is striding into a maelstrom, provoking unusual tumult and disquieting turmoil in an American capital that has been the scene of tumult and turmoil not seen for nearly a half century.

Indeed, not since the Watergate crisis of 1972-1974 has Washington faced the questions – and perhaps the crisis – that Mr. Barr has provoked with his refusal to appear before the House judiciary committee and to provide unredacted copies of the report special counsel Robert Mueller prepared examining ties between Russia and both the Trump campaign and the Trump administration.

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As a result, Mr. Barr, in his second tour as the chief law-enforcement official, faces the possibility of a lengthy legal battle with House Democrats, a resolution holding him in contempt of Congress, even a constitutional crisis that can only be resolved by the Supreme Court.

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At issue – and likely flaring as soon as Monday – are vital issues involving the separation of powers between the legislative and executive branches of the American government that are the hinge of the political system that the country’s founding fathers sculpted in the glow of the late-18th century Enlightenment. These issues, to be sure, have emerged from time to time in the history of the United States, but ordinarily they are settled by reverting to custom or by striking a compromise.

The Trump administration has been scornful of both custom and compromise, which is why the Barr imbroglio is of such significance. And why it has implications far beyond the contemporary contretemps on Capitol Hill, potentially affecting relations between the White House and Congress long after Mr. Trump, his Republican enablers and his Democratic tormentors have long departed the political scene.

There is neither law nor precedence to provide a reliable road map for the current stalemate. House Democrats want the full Mueller document and Mr. Barr doesn’t want to provide it. House Democrats want to grill Mr. Barr under oath and beneath television klieg lights and Mr. Barr doesn’t want to expose himself to a barrage of questions, most of them unfriendly. And Mr. Trump doesn’t want to co-operate with Congress and doesn’t want his Attorney-General to give them an inch, or the report or a chance be interrogated.

That’s where things stand – pretty much in concrete.

As a result, Mr. Barr faces a a fusillade of legal manoeuvres, including contempt citations that he will probably feel free to shrug off because none of the enforcement mechanisms available to the House will strike him as potent enough to overcome his determination to resist them.

“In a strictly pragmatic sense, his calculation might prove sound,” Laurence Tribe, the renowned Harvard legal scholar, said. “But the price he will pay in the court of America’s moral accounting will be immense. Sadly, Barr seems indifferent to history’s all-but-certain verdict that he has compromised his integrity, his oath and his sacred honour for no noble purpose.”

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Indeed, the actual consequences of a congressional resolution of contempt are unclear and given the Republican majority in the Senate the only avenue for Mr. Barr’s removal, congressional impeachment and conviction, is basically off the table.

In the Obama administration, attorney-general Eric Holder was cited for contempt, also for refusal to provide information. The contempt resolution, however, could not be enforced by criminal proceedings because such proceedings must be brought by the Justice Department itself. That’s the precise situation Washington faces this week.

“It was not until three years later,” Robert Post, former dean of the Yale Law School, said, “that a federal judge ordered Holder to hand over some of the documents he had been withholding.”

While the struggle between Mr. Barr and his House inquisitors is not without precedent, Mr. Trump’s broader refusal to co-operate is a reflection of the contempt for political norms that has been the hallmark of his presidency.

“There are well-established understandings to work through these separation-of-powers issues,” said Timothy Naftali, the Montreal-born former director of the Richard Nixon Library. “Each branch has to think through the legitimate needs of the other branch. When the President says that Congress doesn’t need anything from him and that it is getting nothing from him, he is ignoring tradition.”

That is almost the precise language that Jerrold Nadler, chairman of the House judiciary committee, employed in his letter last week to Mr. Barr.

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“Accommodation requires negotiation that takes into account the legitimate interests of both Congress and the [Justice] Department,” the New York Democrat wrote, arguing Mr. Barr’s refusals were a “departure from accommodations made by previous Attorneys General of both parties.”

This crisis will continue into this week. But it won’t be resolved this week, and indeed the principles involved may never be fully resolved.