The country's Supreme Court recently ruled that a decision by Parliament was needed to cement the intended "Brexit," the common name given to the initiative to leave the decades-old consortium after a nationwide referendum resulted in a majority of voters expressing their preference to Leave.

The Supreme Court, meeting with its full complement of 11 judges for the first time ever, ruled 8–3 that the 1972 European Communities Act, which ushered the U.K. into the EU in 1972, when it was the European Economic Community, stipulated that Parliamentary approval was necessary.

Since the Brexit vote, the prime minister who engineered the referendum, David Cameron, has resigned and then-Home Secretary Theresa May was named Conservative Party leader and prime minister. May has made a clear case for the Government's going ahead with Brexit, following the wishes of the referendum, even though it was binding and even though the majority was slim.

The Supreme Court ruling was itself a decision to uphold a similar decision handed by the High Court in November 2015. The key argument by the Government was that it had royal prerogative to act with the requirement of a law passed by Parliament.

The Supreme Court also said that approval was not needed from the devolved governments of Northern Ireland, Scotland, and Wales.

The vote to officially sanction Brexit must be passed by a majority of both the House of Commons and the House of Lords.