The debate* was a strange one, centering around clause 18, the sovereignty clause. As the clause stands, it basically reaffirms the UK legal position that EU law applies in the UK because UK law (in the form of the European Communities Act 1972) says so. The ultimate decision is parliament's, therefore parliament remains sovereign. However the debate obviously contains several competing strands and ideas which see sovereignty in their own ways. It's incredibily hard to define them and tease them out, as they seem to be mashed up. I'll briefly look at some of the points raised (or perhaps half-raised unknowingly by some parliamentarians).
Everyday Absolutists v Ultimate Absolutists.
PS was sometimes defined as "could the UK opt out/disapply an EU law it doesn't like"? The different contributions seemed to indicate 2 lines of thought. 1. Yes, as we can ultimately withdraw from the EU. 2. Yes, we could pass an explicit law disapplying whatever we don't like (in legal terms inserting a provision that the ECA 1972 didn't apply, and it was enacting something different to the EU law). Both, technically, are correct, but the second option would place the UK in breach of EU law and it would be liable to fines - with the matter only being finally settled by withdrawal or the UK accepting the EU law.
Sadly it was only MacShane MP who highlighted that compliance is supposed to be a reciporcal act, using the fact the French had to let in British beef under EU law during the mad cow disease crisis when Commonwealth countries were rejecting it. EU law is not meant to be a pick-'n'-mix affair.
In any case, neither position would have been affected by the amendements either way.
Political reality Constitutionalists v Common Law "radicals".
This was the big debate, and the reason for the introduction of the proposed amendments. Bill Cash is seemingly worried about the power of the judges regarding parliamentary sovereignty. The problem is that Parliamentary sovereignty isn't actually written down anywhere. Of course, it's often said that the UK has an unwritten constitution, but large parts of it are written down; just not in the same place.
There seem to be 2 schools of opinion on the matter. First is the Fundamental Constitutional Principle one, which considers the principle to be outside of the common law (judge-made law) because it was the result of historial events (essentially parliament fighting the monarchy and winning). The second school (increasingly dominant), considers the doctrine to be a common law principle. This matters because the Common Law is an evolving body of judge-made law, where judges interpret and adapt the law. So if PS is part of the Common Law, that means that judges can interpret and adapt it - which is what Cash is worried about, and why he wants to exclude judging from deciding this constitutional matter.
PS is under some preasure from the courts, though there has been little direct conflict yet. In Thoburn v Sunderland City Council, (decided in a relatively low court) it was suggested that some Acts of Parliament should be held to be higher than others (such as the Human Rights Act 1998 and the ECA 1972), so they cannot be affected by implied repeal, but would have to be expressedly repealed by Parliament. This wasn't part of the effective ruling, but obiter, but if accepted it would be a change to PS, as a more recent Act wouldn't impliedly repeal a "constitutional" Act if it conflicited. More recently, in A v Jackson, it was suggested (again in obiter) that PS was a general rule and no longer absolute. The ruling was in the House of Lords (now the Supreme Court), and it was considered that if Parliament breached the rule of law, the courts may not adhere to PS.
Cash wants to prevent the courts from changing the concept of PS, so he wants to set it out in statute. As the Bill is on the EU, and not a general sovereignty Bill, this can't be done in totality, so he attempted to start restricting the courts' role in PS in the area of EU law first.
In some ways I'm reminded of the debates surrounding the constitutional role of the French Parlements (which were big general courts) in the French constitution before the French Revolution. Some Parlementaires wanted to push the idea that they limited the power of the absolute monarchy. As Louis XV retorted:
"...authority can only be exercised in my name... and never be turned against me. For it is to me exclusively that the legislative power belongs without qualification or partition." [Taken from Simon Schama's Citizens, p.87-88.
Obviously it's nowhere near a neat parallel - the UK is a representative democracy, after all - but there does seem to be the idea, gaining ground in recent years, that the courts could limit the Parliament (which claims to be absolute) if it breached the rule of law. The rule of law is a vague concept, but it may have recently gained more legitimacy simply by being recognised as a pre-existing Common Law principle by Parliament in the Constitutional Reform Act 2005. (Indeed, protecting the rule of law is key to judicial concerns, so I suspect that their tentative moves towards adapting the PS doctrine is more as a result of recent anti-terrorist legislation than any influence the EU may have had).
I've spent far too long today reading about this, but naturally the question is complicated and you would need to deeply research this before you could really take a stab at an answer. However, I think I'll give my - perhaps crudely formed - thoughts on this. I am pretty firmly in the Common Law Radicals camp. Though PS isn't rooted in case law or a Parliamentary Act, I have trouble accepting that it should simply be regarded as a Fundamental Constitutional Principle because it was a political reality once political power shifted from the monarch to the Parliament (or, more accurately, from the Crown to the Crown-in-Parliament). It doesn't rest easily with me that the fundamental constitutional principle should be rooted in the argument "might makes right", or even "political reality makes right", with no reference to law - can there be a fundamental constitutional principle that's beyond the law?
More satisfying for me is the idea that PS is part of the Common Law. Courts have, after all, made pronuncements on PS, and if the suggestions in Thoburn or A v Jackson were accepted, then the courts would be changing and shaping the principle. (Ironically many MPs for the amendments cited Lord Justice Laws in Thoburn as supporting their side of the debate because he made it clear that the appliability of EU in the UK was a matter for EU law, yet his obiter thoughts would imply that PS is a Common Law principle!).
Having PS as a Common Law principle raises the problem that judges would have influence over such an important area of the law, but then is having a whipped Parliament in sole, unchecked, charge a better option? In my opinion it is not. A qualified principle of supremacy would mean that the judiciary would be a stronger check on Parliamentary power - but it wouldn't mean that the judiciary takes over all legislative power. Ideally the UK would adopt a constitution vesting sovereignty in the people rather than the Parliament - which brings us to the final strand.
Parliamentary Sovereignists v Popular Sovereignists.
The Bill is intended to make referendums on transfers of power to the EU mandatory. This goes against PS in that it makes the decision the people's, and not Parliament's, and it is intended to be a permanent feature of the constitution - in other words binding its successors (though Parliament could repeal the legislation if it wanted). This shows the political confusion over PS: some politicians obviously equate Parliamentary Sovereignty with popular sovereignty (where the people are sovereign), when they are politically and legally distinct ideas. Indeed, this part of the Bill could cause adaptation of the doctrine of Parliamentary Sovereignty by the courts! To quote Professor Paul Craig, who was one of the legal academics who gave submissions to the European Scrutiny Committee (of which Cash is the chair), at page 23 (PDF):
"How far is a decision whether or not to hold a referendum a legal question, amenable to judicial review,
and how far a political question? The relevant considerations in answering this question are as follows.
(a) The EU Bill is framed in mandatory language. The holding of a referendum is not a matter within the
discretion of the government. It must be held where mandated, [...]
(b) The principal difficulty is that if Parliament enacts a statute approving the Treaty amendment or Article 48(6) Decision without holding a referendum then any judicial review action would be challenging this primary statute. A legal action would run into traditional sovereignty reasoning: the courts do not review the validity of primary statutes in the UK. There are nonetheless two possible ways to surmount this objection.
(i) An aggrieved citizen or MP might try to frame an HRA case, arguing that denial of the referendum violated one of the Convention rights brought into UK law by the HRA. The court would then review the Act of Parliament approving the Treaty amendment without the referendum pursuant to HRA sections 3–4.
(ii) An alternative would be to argue that while the courts will not review the validity of primary statute on substantive grounds, they can do so in relation to arguments of manner and form. This is the “New View” of sovereignty advocated by writers such as Jennings, Heuston and Marshall, who contend that if, for example, an Act of Parliament specified that it could only be amended or repealed by a two thirds majority, then a later statute that made such change by a simple majority should not be recognized by the courts because it did not comply with the conditions for its enactment. It might be argued that the referendum requirement in the EU Bill is, by analogy, a manner and form condition, such that if a later statute were enacted without a positive vote in a referendum then the later Act of Parliament should not recognized by the courts. This reasoning is reinforced because of the wording of Clauses 2(2) and 3(2). The UK courts have not directly pronounced on the reasoning underlying the New View in relation to a case concerned solely with the UK."
This Bill probably highlights tha problems and pressures of having (and trying to maintain) a point of absolute power within a system of devolved government and within the context of supranational and international law. It will be interesting to see if the British constitution can successfully evolve to deal with the legal and political challenges of the modern world, and a modern Europe, or if a more radicial break with the past is needed.
*[Hat tip to Nosemonkey for the debate link].