The Supreme Court was told Prime Minister Boris Johnson prorogued Parliament to avoid scrutiny and saw MPs "as an obstacle" to Brexit.
The UK's highest in London began a three day hearing of appeals of two separate challenges brought in England and Scotland to the prorogation of Parliament.
Eleven Supreme Court justices were asked at the start of an historic hearing on Tuesday to declare Mr Johnson's decision as unlawful.
Later in the session, the court was told the PM would comply with the ruling it makes.
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