Brexit latest: Top UK court to decide if Johnson broke the law by suspending Parliament

Britain's Supreme Court heard arguments Tuesday about whether Prime Minister Boris Johnson's decision to suspend Parliament is legal.

The suspension -- from Sept. 9 to Oct. 14 -- is due to end prior to the Oct. 31 Brexit deadline. The court's ruling may go a long way to determine when, how and if Brexit happens. Voters, in a 2016 referendum, decided by a thin margin that Britain would leave the European Union.

The Supreme Court is hearing the case on appeal after a lower court -- the Court of Session in Edinburgh -- last week ruled in favor of Parliament, saying the prime minister's controversial suspension was “unlawful because it had the purpose of stymieing Parliament" and was therefore "null and of no effect." Prior to that ruling, however, England's High Court had ruled in favor of Johnson, saying that his suspension of Parliament was not a matter for the courts.

Protesters hold banners outside the Supreme Court in London, Tuesday Sept. 17, 2019. (AP Photo/Matt Dunham)

Johnson claims that he suspended Parliament in order to break the UK's political gridlock. Meanwhile, his opponents in Parliament claim he is stalling, strategizing and trying to reduce the political heat he has been taking over the possibility of leading Britain out of the EU without a deal.

Supporting the legal challenge to the prime minister's suspension of Parliament in writing in the Supreme Court were some notable people and governments, including former British Prime Minister John Major, the government of Wales and the government of Scotland. The EU says that the biggest impediment to Johnson and Parliament making a Brexit deal is how the situation with the border with Ireland would be handled, if and when England is no longer part of the EU.

At least one prominent Northern Irish peace activist, Raymond McCord, whose son was killed during "The Troubles," a conflict in Northern Ireland that began in the late 1960s and lasted about 30 years, is also supporting the legal challenge against Johnson in the Supreme Court. He wrote that peace in Ireland would potentially be jeopardized as a result of the fallout if Johnson follows through on his threat to take England out of the EU without a deal in place.

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The Associated Press contributed to this report.