Was the EU referendum advisory?

"In the end, the argument comes down to different visions for democracy in the United Kingdom. The conventional view is that ultimate political power lies with Parliament. The High Court came to its conclusion that the referendum was not legally binding guided by “basic constitutional principles of parliamentary sovereignty and representative parliamentary democracy”.

Cameron, PM at that time, said that he would accept the decision of a referendum.

The law may say that a referendum was not binding, but the government of the time agreed to be bound by it.
Admittedly Cameron, on getting the 'wrong' result, then jumped ship!