The UK Supreme Court has ruled that Prime Minister Boris Johnson’s controversial decision to suspend parliament was unlawful, HuffPost reports.

The president of the Supreme Court, Lady Hale, announced that the court’s judgment was the unanimous judgment of all 11 justices, adding the case is a “one-off,” having come about “in circumstances which have never arisen before and are unlikely to ever arise again.”

The prime minister “prorogued” parliament for five weeks at the start of September, arguing the suspension would allow him to set out a new domestic agenda in a Queen’s speech.

But critics accused Johnson of trying to escape scrutiny in the run-up to the Oct. 31 Brexit deadline, with MPs not due to return to Westminster until Oct. 14.

The Supreme Court judgment comes after challenges to the prime minister’s decision resulted in different rulings at courts in England and Scotland.

The Court of Session in Edinburgh ruled that Johnson’s suspension of parliament was “unlawful” following a case brought by a group of around 75 MPs and peers.

However, a challenge by businesswoman Gina Miller in the High Court in London was unsuccessful.