There has been much discussion of David Cameron's proposal to enact a law requiring a UK referendum before any new European treaties can take effect. Obviously there must be also be some repatriation of powers from Brussels in areas where we feel our sovereignty is unnecessarily and unacceptably compromised, and the proposed law will do nothing to achieve that. But there are three vital areas which the Cameron law will protect from future encroachment.
There will be no unified European foreign policy without a new, post-Lisbon treaty. There will be no unified European army under European command. And there will be no Europe-wide system of taxation decided in Brussels and levied equally across the EU. Any of these would require a new treaty, and such a treaty would require UK citizens to assent to it in a referendum.
The point is that there are European politicians with such ambitions, people who want to turn the EU into a unified super-state to match the continental scale of the US and Russia. This is one reason behind the almost hysterical abuse heaped on the proposal by some European ministers. They have spotted, correctly, that it will put a permanent limit on their centralizing ambitions.
Much of Europe's progress towards "ever closer union" has been achieved, often by stealth, by the political class of Europe over and against the wishes of ordinary citizens of European countries. That will change once the new bill is passed, enfranchising British voters by giving them a direct say in any future moves. While the proposed law will not solve the problem of present and previous European intrusion into affairs that can and should be decided in Britain, it will draw a line in the sand, making it difficult for more UK sovereignty to be lost without the direct consent of its citizens.
Check out Madsen Pirie's new book, "101 Great Philosophers."