Lord Carloway, Scotland’s most senior judge, has said the advice given by the British government to Queen Elizabeth II concerning the prorogation of parliament was "unlawful".
The judges made the ruling at the highest court of appeal in Edinburgh on Wednesday morning.
A group of approximately 70 M.P.s brought the case before the courts in Scotland last week during which time Judge Lord Doherty ruled that Boris Johnson's decision to suspend parliament was lawful.
However, the same group appealed to the highest supreme court in Scotland and the ruling was overturned by three judges who ruled the proroguing of parliament unlawful.
Then, on Tuesday, three judges of the Inner House, the supreme civil court in Scotland, disagreed with Lord Doherty's ruling.
The U.K. government plans to appeal against the latest ruling to the Supreme Court in London on Tuesday.
The decision was hailed as "historic" by Scottish National Party M.P. Joanna Cherry who was heavily involved with the case.
At the hearing, Judge Lord Carloway told the court: "We are of the opinion that the advice given by the Government to her majesty the Queen to prorogue parliament was unlawful and that the prorogation itself was unlawful."
Campaigners said their understanding is that parliament can now reassemble if it so wishes.
The UK Government said it would appeal against the court's decision.
"The UK Government needs to bring forward a strong domestic legislative agenda. Proroguing Parliament is the legal and necessary way of delivering this," said a spokesman for the government.