In democratic states the world over, the tussle between governments and parliaments over who gets the final say on issues is a universal feature of political life. In the UK, by historical circumstance, the reach of the government in this regard is known as the "royal prerogative". On Thursday it was firmly circumscribed over Brexit by the High Court.
Each state sets a different limit. Two weeks ago we were all preoccupied by the right of the Wallonian regional parliament to veto the EU's trade deal with Canada, a possibility denied to members of our own Oireachtas because the Government here has the power to make trade deals. In the US, control over sending troops abroad – though not of waging war – is a prerogative strongly defended by the president from Congress, while in Ireland the Dáil has to approve any such deployment.
Traditionally the British royal prerogative has extended to allowing the government the right to negotiate and approve international agreements, and so it expected to have a free hand on triggering article 50 to start the Brexit process. But “hold your horses”, the High Court said.
The 1972 European Communities Act, which gives effect to Britain’s EU membership, it argued, is a matter of domestic law, not of foreign policy. Lord Justice Thomas insisted that the rights given by parliament in the act could not be taken away by the government – only by parliament.And an appeal to the Supreme Court, to be heard as soon as December, is unlikely to overturn that reasoning.
The decision is an important victory for parliamentary sovereignty, although it will pose complications and difficulties for PM Theresa May and injects a whole new level of uncertainty into the Brexit process. Whether she will have to set out, and seek approval for, her full negotiating strategy before the Commons is unclear, although unlikely.
But hard Brexiters know that their majority in the country is not reflected among MPs and wonder what constraints a Commons majority of Remainers and supporters of a “soft” Brexit will be able to impose on negotiators.