Parliament had the opportunity to push for legislation to be put in place to trigger Article 50, but choose not to, the attorney general has told the Supreme Court.
On the first day of what is due to be a four-day hearing, Jeremy Wright argued the government's wish to start the UK's formal withdrawal procedure from the EU was not an attempt to disregard parliamentary sovereignty but, rather was respecting the message sent by parliament staying silent on the matter.
"The triggering of Article 50, we say, will not be an exercise of the prerogative on a whim or out of a clear blue sky," the attorney general said.
The attorney general noted that, while the claimants who brought the initial case to the High Court earlier this year had argued they were doing so to protect parliamentary sovereignty, "parliament can stand up for itself".
Wright added that, just because government did not feel it must approach MPs for fully legislative sign off on Article 50, it did not mean "parliament will not be closely involved".
Today's hearing is an appeal of a decision last month from the High Court, where a trio of judges found in favour of a group of claimants arguing the UK's unwritten constitution did not allow government to trigger Article 50 without first having an act of parliament in place.
Although those who brought the case have staunchly maintained they do not intend to overthrow June's Brexit vote and do not have a political motive, they have unfortunately been subject to abuse and threats.
Opening today's hearing, Lord Neuberger, president of the Supreme Court, condemned such behaviour.
"Threatening and abusing people because they are exercising their fundamental right to go to court undermines the rule of law," Neuberger said. "Anyone who communicates such threats or abuse should be aware that there are legal powers designed to ensure that access to the courts is available to everyone."