Varney contradicts Alexander on corporation tax

When Labour’s Holyrood leader Wendy Alexander announced her devolution proposals last month, she cast some doubt over whether the Scottish Parliament could legally be given control of corporation tax:

We should approach this with an open mind but there are constraints
here.   Some suggest VAT for example but EU rules appear to preclude
VAT variation within a state.   So it could not be a candidate for
devolution, although could be considered for partial assignation.
Likewise the issue of Corporation tax variation within a state also
raises issues of compliance with EU rules (the Azores judgement) as
well as potentially distorted transfer pricing. (Scottish Labour)

In his review of taxation in Northern Ireland, Sir David Varney seems to have clarified the Azores issue:

A move to a differential corporation tax rate for Northern Ireland would be possible in principle. However, it would involve legislative changes and legal issues would affect the design of such a scheme. Also, the fiscal consequences of such a move would have to be borne immediately by the Northern Ireland Assembly. (Varney Review)