Could Brexit spark a devolution battle?

Carwyn Jones has was warned of a "constitutional crisis"

I'm in Brussels for Carwyn Jones' meeting with Michel Barnier, the EU's chief Brexit negotiator, writes guest blogger Daniel Davies.

Perhaps the first minister will get a better reception here than he feels he's had in London.

UK ministers think they have been very accommodating. Brexit secretary David Davis says they've "bent over backwards" for the devolved administrations.

And yet Mr Jones complained this week about letters to Downing Street going unanswered and the difficulty of arranging meetings.

He also put AMs on notice of a possible "constitutional crisis".

'Holding pattern'

Today the UK Government has publish its European Union (Withdrawal) Bill - previously described as the Repeal Bill - copying EU regulations and pasting them on to the statute book.

As part of the "bending over backwards strategy" a draft copy has been sent to Cathays Park. But the Welsh Government is unimpressed.

At issue is what happens to powers returning to Brussels in devolved policies.

All sides say new UK-wide rules - on paying farm subsidies, for example - will have to be agreed upon.

But while the Welsh Government thinks the powers should come directly to Cardiff before talks start, the UK Government has talked about powers stopping off in London en route in a "holding pattern".

At least that was the plan before the general election. If the bill published today doesn't satisfy the first minister, he'll invite the assembly to withhold its legislative consent.

That would be a symbolic defeat for the UK Government, but Theresa May need not necessarily pay much attention. Such votes are not legally binding on Parliament.

David Davis says UK ministers have worked hard to involve devolved governments in Brexit

Possibly of more interest is the Welsh Government's threat to publish a mini repeal bill for Wales - the Continuity Bill. This will transpose EU rules that apply to the assembly into Welsh law.

What will happen if the UK Government ignores the Continuity Bill and carries on regardless?

Mr Jones told AMs this week: "It's the issue of whether the UK Government and House of Lords particularly would see it as constitutionally proper to overturn legislation that's passed in this assembly, thus prompting a constitutional crisis."

If he pushes ahead - and a lot of preparatory work on a Continuity Bill has happened behind the scenes - Mr Jones will publish the bill in the autumn. He would also ask to change the Assembly's rules so legislation can be sped through before the repeal bill passes in Westminster.

As one of his aides put it to me, with so much work on their hands, why would UK ministers want to "pick a battle on the home front as well"?