The controversy in British politics about the suspension of Parliament, known as prorogation, is unprecedented and significant. The dispute is different from the usual and often confected accusations about improper use of political power: The issue at stake is a fundamental one, and it may mean the United Kingdom is moving toward a constitutional crisis.

The background to this is, of course, the departure of the United Kingdom from the European Union. That exit, which has already been twice postponed, is set for Oct. 31. The departure is the default position. It is what will happen by automatic operation of law unless something stops it.

The intention had been for this departure to be accompanied by a comprehensive withdrawal agreement providing for practical issues that include residency rights for affected citizens and the applicable law for ongoing transactions. In November, British and European negotiators finalized a draft agreement.

The deal, however, has proved unacceptable to Parliament, and it has been rejected three times, including two of the heaviest government defeats in British history. The main, but not the only, sticking point is the “backstop” arrangements affecting the border between Ireland and Northern Ireland. This backstop would mean that if the United Kingdom and the European Union fail to agree on a new trading relationship after departure, then there would be continuity in cross-border commercial activity.

The implication of the backstop, however, is that the United Kingdom may stay within the European Union’s single market and customs union after departure, which makes leaving the European Union pointless in substance. Brexiteers who oppose the backstop have a point: It would be a Brexit in name only. This and other concerns have meant that many members of Parliament are adamant that the deal cannot be endorsed. Failure to get a deal through led to the last prime minister, Theresa May, being forced from office.

European leaders, on the other hand, are adamant that this backstop insurance is necessary. They, too, have a point: The United Kingdom has shown throughout the exit negotiations a lack of seriousness and good faith and so the European Union, on behalf of the Irish government, is insisting that the foreseeable consequence of there being no new trading agreement in time is set out in a legally meaningful way.

That contradiction cannot easily be resolved. There have been efforts to show how “alternative arrangements” could address the Irish border issue, but few are convinced, and there is no concrete detail. It is unlikely that a resolution can be found before the Brexit deadline or, indeed, at any time. The problem may not have a solution.

But Prime Minister Boris Johnson has stated that, despite there not being a deal in place, the United Kingdom should leave the European Union on Oct. 31. For him and his supporters, the delay to Brexit has been long enough, and this is how the June 2016 referendum result should be honored: Departure is more important than the terms governing it.

Johnson and his government do not, however, control a working majority of Parliament on that question. And just as Parliament is against the deal Johnson’s predecessor negotiated, it is also against a “no deal” departure. The magnitude of the predicament that no deal would cause is overwhelming: For example, supply lines for items such as medicine and automobiles would be disrupted if not destroyed, and millions of people would have uncertain legal positions.

And it is in this context that the significance of Johnson’s use of the prorogation device can be seen. Prorogations usually are not controversial: They mean one parliamentary session will end and another will begin.

But this prorogation means Parliament cannot function: It is closed as a means of scrutinizing the executive and cannot pass legislation. This is different from a mere recess where Parliament happens not to sit. Here, Parliament will be prorogued for five weeks in the crucial but short period before the Brexit date.

The only reason to do this is to make it far more difficult for Parliament to prevent a no-deal Brexit. Other than by revoking the decision to leave or agreeing to the deal, the only way a departure can be avoided now is by the United Kingdom and the European Union agreeing to a further extension (which, of course, the European Union may not go along with).

And in view of Johnson’s determination that the United Kingdom must leave the European Union regardless of a deal, this extension can only come through Parliament acting to remove the prime minister or enacting new legislation, both of which would be difficult before Oct. 31 even without the prorogation.

This is why the prorogation is being seen, rightly, as a direct assault by the executive on the rightful powers of the legislature. And this is not the view of liberal opponents but of many senior Conservative politicians. Lord George Young, the only surviving minister from the Margaret Thatcher era, has resigned on this basis. Former prime minister Sir John Major, who succeeded Thatcher, is going to court to litigate against this constitutional imposition.

Fundamental attacks by one part of the state against another are rare in modern democracies, or at least they should be. Constitutional law should be dull, not this exciting. A happy political system does not have many constitutional cases. But the pro-Brexit government of Johnson is desperate, and it has adopted this as a means to force through its policy against a majority in parliament.

The ploy may not work: There are just enough days for a determined Parliament to ensure there is not the disaster of a no-deal Brexit, but there is no guarantee they will succeed. What will linger either way is the deep sense of wrongness, of the government attempting to unfairly (if not unlawfully) game the constitution so as to prevent legitimate checks and balances. This will not end well, whatever happens.

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