In his statement to the Westminster Parliament presenting the white paper responding to the Calman Commission, Jim Murphy made it clear that the new arrangements would require a new Scotland Bill, which will be introduced by Labour after a general election. (The Conservatives have reserved their position: they refuse to be committed on timescale at all and insist on being able to introduce their own white paper, though Ken Clarke says this might be done in the first year of a Tory government.) It may well be that these proposals will never get the chance to turn into legislation – much depends on the outcome of the UK general election, who forms the government afterward and what they propose to do.
If it does result in new primary legislation, then it will be subject to the Sewel Convention. The convention requires that any change to the powers of the Scottish Parliament or the Scottish Government (as well as substantive legislation on devolved matters) obtain the consent of the Parliament. The convention stops the UK Parliament making such changes unilaterally. That convention isn’t explicitly recognised by the UK Parliament, though complying with it is UK Government policy (see Devolution Guidance Note 10, available here). It’s also embodied in Holyrood’s standing orders (see Chapter 9B, available here). Even if the UK Government wanted to ride roughshod over that convention (which is unlikely; it praises the Convention in paragraph 3.5 of the white paper), this is going to have to be considered on the floor of the Scottish Parliament, possibly in multiple votes.
It will be the most complex legislative consent motion so far – and by far the most contentious. The Scottish Government’s response to Calman makes it clear that it opposes at least provisions that will need to be in the bill giving UK sole control of matters relating to all health professions. The Scottish Government also opposes the provisions relating to a single set of rules about charities and altering the position regarding liquidation of companies, though it’s not clear from the white paper if these will need legislation or not.
The question is how much unease there is among the Liberal Democrats and Scottish Labour. The Lib Dems are evidently unhappy about the slow pace of progress, and may have more substantive concerns in private. Some people in Labour may well share those concerns too, knowing that it doesn’t offer politically what’s needed to give Labour a strong answer to the SNP in constitutional debates. But to get the new Scotland bill through, both parties are going to have to vote in favour of it at Holyrood. Will they in fact be able to do so in a united fashion? Or will some MSPs split, in what might be a close vote, and try to block the bill?
Even if Labour should be in a position at Westminster to deliver on their commitments, it’s not self-evident that the Scottish Parliament will agree. If we ever see it, it will be a fascinating debate.