Last week, British Prime Minister Boris Johnson decided to “prorogue” Parliament for the next few weeks. So what is prorogation? Does it have any historical precedent or constitutional implications?

To prorogue is to formally end a session of Parliament. Johnson did this to make it harder for opponents to affect his actions on Brexit, limiting the amount of time they have to debate the withdrawal from the European Union or pass new laws on the issue. In proroguing Parliament sooner than expected, Johnson is updating an old political trick. As my research shows, kings used to prorogue Parliament regularly in the 17th century to limit Parliament’s powers or to press it to do things that the monarch wanted it to do.

Proroguing has a long history

In the late 17th century, suddenly proroguing a session of Parliament was one of the monarch’s most powerful tools to influence policymaking. In 1678, King Charles II said to the House of Lords, “I intend therefore to prorogue them for some short Time, in Hopes they will consider better what they ought to do at their Return.”

Proroguing became common during a period of intense political conflict that stretched from 1660 to 1690. Slightly more than half of all sessions of Parliament from 1660 to 1690 were suddenly closed by the monarch. Parliament might be closed for less than a week or as long as three years. This affected legislation. During the period when a session is prorogued, whether sudden or expected, all legislation that hasn’t yet been approved by the House of Commons, the House of Lords and the monarch automatically fails.

Just like today, it was used to undermine Parliament

Johnson has decided to prorogue Parliament to stop its current E.U. legislation and introduce his own when it reopens in five weeks. Similarly, late-17th-century monarchs Charles II and James II suddenly prorogued sessions to interfere with or influence bills on major fiscal and constitutional issues of the day. For example, when Charles II sought parliamentary funding to fight wars against the Dutch Republic, he interrupted proceedings via prorogation if Parliament spent time on other debates. The monarch also suddenly closed sessions when concerned about other constitutional issues, such as Parliament’s attempts to influence the succession of the monarchy.

Prorogation damaged Parliament’s ability to get its work done

The sudden closures “killed” the bills that were against the monarchs’ interest. But they also ended all the other legislation that Parliament was working on during the session. Time is a very scarce resource for legislators. Knowing the session’s end date helps organize their legislative program. But those plans could be upset if Parliament were to end before the expected date. My research on the 17th century shows that proroguing was legislatively costly when it happened, causing bills to fail. Specifically, I show projects that allowed land to be sold or used in new ways failed because of the sudden closures of Parliament. These bills that had to be reintroduced in the next session displaced new projects.

That may be true this year, as well. Some commentators have discussed the unintended legislative costs of the 2019 parliamentary prorogation. Depending on its priorities and the current status of its legislative work, Parliament may be able to speed up the passage of some bills to ready them for approval on the date of prorogation in mid-September, while others will have to be restarted next session.

Parliament’s legislative agenda is broader in economic scope than it was in the 17th century, and some rules have changed. For example, some public bills can be carried over into the next session. One analyst noted that, as of March 2019, public bills such as the Trade Bill and the Financial Services Bill “would fall if they couldn’t be rushed through.” Others, such as a bill to regulate plastic pollution, appear set to fail because of the government’s functioning and not because of the bill’s merits or other political considerations.

Sudden proroguing died for nearly three centuries after Parliament increased its powers

The reliance on proroguing Parliament raised constitutional concerns about the balance of power in the English government during the 17th century. Members of Parliament sought to protect parliamentary rights from the monarch’s interference, including proroguing. Historian Betty Kemp, in her 1971 history of parliamentary procedure during this period, describes how in 1667 the House of Commons created a committee to find out what “doth obstruct the Proceedings of the Public Business of the House and what the ancient use and Practice of the House hath been, for the Dispatch of the public business.”

The systematic use of sudden prorogations stopped shortly after the Glorious Revolution of 1688. James II was forced to abdicate after not respecting parliamentary rights: He suddenly prorogued Parliament in 1685 and did not call it back into session for three years. William and Mary, rulers of the Dutch Republic (Mary was the daughter of James II and, therefore, in the line of succession to Britain’s monarchy), invaded England and were installed as co-monarchs. The Glorious Revolution introduced constitutional and political changes that better protected Parliament’s constitutional rights, as political scientist Gary Cox has shown. The last sudden prorogation of the period occurred in 1690.

Obviously, Johnson’s proroguing is unlikely to lead to a new invasion of Britain. But Parliament has more strategies available from history to defend its decision-making power from imperious prime ministers. For instance, Commons Speaker John Bercow reached for a precedent from 1604 to refuse a third vote on the Brexit deal in March.

Kara Dimitruk is a postdoctoral fellow in the department of economics and Laboratory for the Economics of Africa’s Past (LEAP) at Stellenbosch University in South Africa.