The 1972 European Communities Act means that for certain subjects European Statute takes precedence (hence parliament is not supreme for that purpose). If we are going to repeal this act we should do it explicitly. Incidentally the Lisbon Treaty allows leaving the EU. I am still likely to vote against 3rd Reading on the basis of the absence of the referendum, but I do support our membership of the EU and the 1972 Act (passed when I was 12).
Ok, the news that John Hemming intends to vote down the Treaty may not be earthshattering, but it signals that the LibDems problems on this issue are far from over, as their votes in the House of Lords will amply demonstrate.