Carwyn Jones dropped in on EU chief negotiator Michel Barnier today before issuing a joint statement with Nicola Sturgeon condemning the "naked power grab" of the legislation. That statement prompted UKIP to accuse Mr Jones of "crossing the road to pick a fight".
Both first ministers say they won't recommend the Bill in its current form gets the legislative consent of AMs and MSPs.
Not for the first time the Welsh first minister is warning of a "constitutional crisis". And not for the first time in recent weeks he has put Theresa May's government on the back foot.
The first ministers' "power-grab" is what the UK government sees as an essential way of ensuring Welsh farmers (among others) can continue to trade after Brexit before UK-wide frameworks are decided. The UK government has put together a factsheet on the Bill and devolution that puts its side of the argument.
Welsh Secretary Alun Cairns said: "I have got to look Welsh farmers in the eye and tell them yes they will be able to have the opportunity to continue to sell their Welsh lambs in France, and across Europe.
"But in order to get to that position we need this framework in place. That is fundamental to the trade arrangements." Discuss.
In other news, Wales's youngest MP has delivered his maiden speech. Ben Lake, 24, gave a traditional speech that included a generous tribute to his Liberal Democrat predecessor Mark Williams: "He gained the respect of this House, and the affection of the constituency, thanks to over 12 years of tireless service," said Mr Lake.
"Thousands of people from across the county have benefited from his advice and assistance, and I hope to continue with his good work. I wish him, and his family, the very best for the future."
As is traditional, he spoke of the delights of his constituency. "We can also justifiably claim to be the capital of Welsh culture," he said. "In addition to housing the National Library and two universities, Ceredigion has two thriving publishing houses in Talybont and Llandysul, and the recently restored castle at Cardigan played host to the first national Eisteddfod in 1176."
He also praised "the emphatic landscape and the famous quick-witted humour of the Cardi" but also noted Ceredigion's challenges. "Several of my predecessors in this House have pointed to the tragic irony that Ceredigion bestows upon its youth an unrivalled education, but offers them a paucity of job opportunities and affordable housing.
"For decades, our county has lost the potential and the vitality of its youth. Around half her young people leave the county by the time they reach 25 years of age."
His speech was relatively uncontroversial, although Bridgend Labour MP Madeleine Moon picked him up on one point.
"I take exception a little bit," she said, "to his suggestion that Ceredigion is the finest place in Wales to go on holiday. Porthcawl is obviously a great seaside town but what I would say I hope his speech has inspired those who are listening to think of Wales as their holiday destination this year."
There's no disguising the frustration in UK government circles over the reaction from Cardiff to its "great repeal Bill" - formally known as the European Union (Withdrawal) Bill.