The Lib Dem Europe Rebellion

Nick Harvey voted against Maastricht, so it's hardly a surprise that he's against Lisbon. But why are he and David Heath hung up on this referendum business? They should just say that no one with any liberal or democratic sense whatever can do other than oppose any further extension of the legislative power of a body which meets in secret and publishes no Official Report, that no party with significant strength in the West Country and in rural Scotland can do other than oppose any EU Treaty that fails to abolish the Common Fisheries Policy, and that throwing out such things is what Parliament is for. What's stopping them?