The Welsh Government will find out today if the Assembly will be given a formal say on the UK Government's negotiations to leave the European Union when the Supreme Court delivers its ruling on who has the power to trigger Brexit.
Theresa May's Government appealed against a ruling by judges in the High Court ruled that it must hold a vote in parliament to trigger the start of the process of leaving the European Union.
Ministers argued that they can begin the process of leaving by triggering Article 50 of the Lisbon Treaty without needing the support of MPs.
The Welsh Government was involved in the case with Wales' legal chief, Mick Antoniw, arguing that not only must Parliament have a say but that it must also consult the National Assembly.
The Consul General also says the process risks changing the powers of the Assembly without the consent of AMs, overriding 'an important constitutional principle.'
During Supreme Court hearings, the UK Government's lawyers dismissed the Welsh Government's arguments insisting that 'the conduct of foreign affairs' has nothing to do with devolved administrations.
They also described the Counsel General's case as a 'tortuous attempt..to generate some relevance of EU law to .. the Government of Wales Act.'
It's thought the UK Government is expecting to lose its appeal and has legislation in four different forms ready to be debated in Parliament. It's not clear what would happen if it needs to seek the approval of Britain's devolved parliaments.
Scotland's First Minister has already said that the Scottish Parliament will hold a vote regardless of the outcome of the Supreme Court ruling.
Yesterday Carwyn Jones and Leanne Wood set out alternative plans for life after EU membership which would see continued full and unfettered access to the single market, something the Prime Minister has signalled that she's prepared to do without.