Constitutional practicability of referendum on EU Constitution

No. (UK has no written constitution) Binding referendum requires a legal implementation as a part of the ratification-process. Consultative referendum can anyhow be held if ordered by ad-hoc-law.

Approval of European Treaties

When the UK joined the Community, accession was preceded by the passing of the European Communities Act 1972 which made the Treaty and the law deriving from it applicable within the UK. Changes of the European treaties that implicate constitutional changes for the UK like the Maastricht Treaty are implemented by amending the European Communities Act 1972.

Approval of international treaties

Treaties are ratified by the Foreign Secretary, acting on the residual authority of the Crown (Royal Prerogative). Parliament has no formal role in treaty-making. Since the 1920’s there has been a constitutional practice called “the Ponsonby Rule” which requires that all treaties subject to ratification be laid before parliament for information and debate. Under British constitutional practice, the passage of the implementing legislation is not formally part of ratification, but it must precede ratification.