The judgement says,
"I would add only this. I approach matters on the basis that it would be destructive of one of the core principles of constitutional propriety and of the mutual trust that is the bedrock of the relationship between the court and the Crown for the Prime Minister or the government to renege on what they have assured the court that the Prime Minister intends to do. As the Advocate General’s note of argument says:
“As already noted, the Prime Minister is well aware of his duty to obey the law, including the frustration principle, and is and will continue to be advised in the
usual way on any issues as to the lawfulness of his proposed actions.”