I know I've mentioned this a few times before, so apologies for repeating myself. But a couple of years ago I took part in a podcast with Andrew Tickell, and I was very surprised when he took issue with my point that it would be perfectly possible to entrench a devolved Scottish Parliament as permanent, and that it isn't strictly true to say that no Westminster government can bind its successors. The example I gave was that the independence of Australia was legislated for by Westminster, and that there's no way Westminster can now abolish Australian independence simply by repealing that law. Andrew insisted that was flatly wrong - in theory, Westminster can repeal Australian independence because the principle of parliamentary sovereignty means that it can do whatever it likes, no matter how absurd.
Having thought about it since, I think that looks at the issue the wrong way round. If Westminster tried to repeal the Australia Act 1986, and if anyone was foolish enough to take that seriously, the issue would be decided by the Australian courts, not the British ones. Australian judges would undoubtedly take the view that the supremacy of the British parliament ceased to have effect in Australia from the moment a law was passed stating that : "No Act of the Parliament of the United Kingdom passed after the commencement of this Act shall extend, or be deemed to extend, to the Commonwealth..." Australia is now subject to Australian constitutional law only.
A similar principle might be said to apply to Scotland in reverse, because the authority of the Westminster parliament ultimately derives from an Act of the pre-union Scottish Parliament, namely the Union with England Act 1707. I believe I'm correct in saying that Scottish judges have previously indicated that some parts of that Act are more entrenched than others, and that the Scottish courts wouldn't necessarily stand idly by if Westminster unilaterally ripped up some of its key provisions.
So there does appear to be legislative language which is strong enough to trump the 'absolute sovereignty of parliament' principle. The million dollar question is whether the beefed-up 'permanence' clause in the Scotland Bill is sufficiently strong to have that effect. This is how it now reads -
PERMANENCE OF THE SCOTTISH PARLIAMENT AND SCOTTISH GOVERNMENT
63A Permanence of the Scottish Parliament and Scottish Government
(1) The Scottish Parliament and the Scottish Government are a permanent part of the United Kingdom’s constitutional arrangements.
(2) The purpose of this section is, with due regard to the other provisions of this Act, to signify the commitment of the Parliament and Government of the United Kingdom to the Scottish Parliament and the Scottish Government.
(3) In view of that commitment it is declared that the Scottish Parliament and the Scottish Government are not to be abolished except on the basis of a decision of the people of Scotland voting in a referendum.
To be fair, I think this does take us a little further forward, because it's now the case that Westminster would definitely have to repeal that Clause if it ever wanted to abolish the Scottish Parliament without a referendum. (The previous wording was the suspiciously tortured "it is recognised that the Scottish Parliament is a permanent part...", which may not even have had any legal effect at all. It was more like commentary than law - "recognised" by who exactly?) So at least it will now be the law of the land that the Scottish Parliament cannot be abolished except by popular vote. The snag is that Westminster will still be free to change that law whenever it likes, and probably won't have to break much of a sweat to do it. I suppose the language is now strong enough that if any attempt at repeal is made, a legal challenge might be launched on the basis that Westminster is attempting to use legislative powers that it has already terminated with the words "are not to be abolished". But that would be a very optimistic challenge, with presumably only an outside chance of success.
The wording of the clause still looks very peculiar to me, and it's hard not to conclude that the Tories' real objective is to look as if they're making the Scottish Parliament permanent, without giving that principle any meaningful effect in law. There are a lot of seemingly redundant words in there ("signify the commitment of", "in view of that commitment", "it is declared that"), and I would be interested to hear from legal experts what message is likely to be conveyed to the courts by those words. If the government are acting in good faith, it's very hard to understand why they've rejected the Australian-style wording of "the power of the United Kingdom parliament to abolish the Scottish Parliament without consent is terminated".
There's a reason why this is important. Just about the only part of The Vow that wasn't couched in incredibly vague language was the promise of permanence. So if the Scottish Parliament's permanence isn't being guaranteed, The Vow isn't being delivered in full. Simple as that.