Judge Lady Hale, along with other 10 top judges, must offer decision whether Johnson’s advice given to the Queen about shutdown was lawful.
SC President Lady Hale, in her opening remarks, said: “That this is a serious and difficult question of law is amply demonstrated by the fact that three senior judges in Scotland have reached a different conclusion from three senior judges in England and Wales.”
She also said the court would make efforts to address all questions but, won’t determine “wider political questions” in relation to the Brexit deal process or cause impact over its timing.
SNP MP Joanna Cherry – a lawyer involved in the Scottish case, told BBC News she was “cautiously optimistic” the SC would uphold ruling.
Although, she said it would be “accepting that it’s possible… for the prime minister of a minority government to shut down Parliament if it is getting in his way”.
Arguing on the government’s behalf on Tuesday, Scotland advocate general Lord Keem told the SC in declaring shutdown “null and of no effect”, the Scottish high court had “simply gone where the court could not go”. He added if SC upholds ruling, Johnson would be willing to adhere “all necessary steps” in order to comply.
Government lawyer Lord Keen QC has said the prime minister was “entitled” to perform as he did and the matter was not for the court.
Lord Pannick QC for campaigners – who are against the move, told the SC it was done in order “silence” members of parliament for five weeks.