In the case at the High Court,
the Government (Secretary of State) did not claim that the referendum by itself
gave it the power to take the
The judges continue by explaining (§106) that a referendum is “only advisory for the lawmakers in Parliament unless very clear language to the contrary is used”, which was not the case in the 2015 Act. They also point out (§107) that Parliament passed the Act against the background of a briefing paper that clearly said that the referendum was only advisory.
So the referendum result definitely did not give the Government a mandate from Parliament via the people.
But does Parliament have to be involved at all? Can’t the people give a mandate directly to the Government?
The answer, under British law, is definitely a resounding “No”. The judges discuss the principle of the sovereignty of Parliament (§§20/23, pages 6/7). They quote (§22) Professor A V Dicey, who wrote “the leading account” of the law of the British constitution. He says: “The judges know nothing about any will of the people except in so far as that will is expressed by an Act of Parliament”. (By “the judges”, he means, of course, the law.) That seems absolutely clear: the “people” cannot give the Government authority directly, through a referendum.
The quotation from Dicey continues: “and would never suffer the validity of a statute to be questioned on the ground of its having been passed … in opposition to the wishes of the electors.” That seems absolutely clear, too: Parliament isn’t bound to follow the result of the referendum – it is perfectly free to decide both whether the result really represents the wishes of the electorate and, more importantly, whether acting on the result would really be in the best interests of the electorate. Parliament is free to decide.