Is David Cameron a Member of Parliament?

One distinctive feature of Britain’s political system is that ministers are required to hold a seat in Parliament to propose legislation and be held to account by fellow lawmakers.

But another is that the government, when it needs to, can produce such a seat more or less out of thin air by awarding the new minister a lifetime place in the Parliament’s less powerful, unelected upper chamber, the House of Lords.

That’s what Downing Street says will happen with David Cameron, who quit his parliamentary seat — as well as the prime minister’s post — after his defeat in the 2016 Brexit referendum.

The maneuver means that Mr. Cameron can return to government without needing to face an election.

It’s not the first time in the modern era that a foreign secretary has been a member of the House of Lords, rather than the House of Commons. Peter Carington, who became Lord Carrington, performed the role from 1979 to 1982 when Margaret Thatcher was prime minister.

The procedure can be a means of placing an expert in a position of power: In 2005, the Labour government at the time gave a House of Lords seat to one of its key advisers on an overhaul of the schools system so that he could become a minister in the education department implementing the plan. (The adviser, Andrew Adonis, later went on to join the cabinet as transport secretary.)

It can also allow for the summoning back of a political figure whose career had appeared to be over. The precedent most often cited for what’s happening with Mr. Cameron is that of Peter Mandelson, who was appointed to the Lords in 2008 to join the cabinet of Gordon Brown, then the prime minister. Mr. Mandelson had quit Parliament several years earlier to take up a post as a European Union official.

Mr. Mandelson’s career also had plenty of twists: He had already twice resigned, under pressure, from the cabinet of Mr. Brown’s predecessor, Tony Blair.

While the situation is not unique, having Mr. Cameron in the House of Lords could cause tensions among lawmakers in the House of Commons as he will speak directly not to them but to an assembly of unelected members of the upper chamber.

Although Mr. Cameron’s return to a top political job stunned Westminster on Monday, it might not have been such a big surprise in previous eras. Since the 18th century, 14 prime ministers have come back to serve in governments led by others.

But in recent decades such moves have been rare. The last former prime minister to return to the cabinet was Alec Douglas-Home, who served as foreign secretary from 1970-74.