Most analysis of, and speculation about, the ‘meaningful vote’ has been from a purely Brexit perspective.

The rights that Parliament has, and at what point, could be critical to the outcome of the Brexit process.

We pointed out a year ago that parties’ and parliamentarians’ pursuit of different Brexit strategies involved efforts to structure the endgame decision-making process in their favour. (The government’s strategy is to offer Parliament a choice between ‘this deal’ and ‘Brexit with no deal’; by explicitly including the framework for the future UK-EU relationship in ‘this deal’, the government’s ‘meaningful vote’ amendment is arguably the latest example of this behaviour.) Today’s debate and votes are thus merely the latest stage in a negotiation that has been underway, through the medium of Parliament’s Brexit debates, for 18 months. Over that time, the direction of travel has been pretty much one way: at her appearance before the Liaison Committee in December 2016, the Prime Minister was unable to say that Parliament would have a vote on any Withdrawal Agreement at all.

Some of the proposals and passion surrounding the ‘meaningful vote’ reflect the internationally and historically unusual nature of the Brexit withdrawal negotiations. In the cases of most international agreements, if one party’s legislature votes it down the status quo prevails; whereas in Brexit, not achieving a ratified agreement is more akin to triggering a sunset clause on the legal underpinnings for all the UK’s interactions with the EU. The prime common concern among parliamentary opponents of the government’s ‘this deal or Brexit with no deal’ approach has appeared to be to rule out the prospect of a no-deal Brexit taking place without Parliament having a guaranteed and explicit say. (In ‘ping pong’ on the EU (Notification of Withdrawal) Bill in March 2017, the Commons rejected a less sophisticated Lords amendment than the present one, which straightforwardly required parliamentary approval for “any decision by the Prime Minister that the UK shall leave the EU without an agreement”). Meanwhile, it is owing to the implacability of the Article 50 end-date, plus the room for dispute about what a parliamentary vote against ‘this deal’ might mean, that the ‘meaningful vote’ debate brings arguments about approval and ratification of any Withdrawal Agreement (i.e. the end of the treaty-making process) together with even more controversial arguments about Parliament’s potential role in directing or mandating government behaviour in international negotiations looking forward.

Leaving the peculiarities of Brexit aside, it will be evident that these arguments have broader, constitutional, significance, and concern Parliament’s role in the making of international agreements.

And they come as the UK is about to embark on a major period of international treaty-making, as it seeks to replicate many of the effects of the hundreds of international agreements (including trade agreements) in which it currently participates by virtue of its EU membership, as well as make new agreements for itself - not least with the EU.

Parliament’s default role in UK treaty-making is weak: under the Constitutional Reform and Governance Act 2010, the House of Commons has only a negative power to delay consent to ratification.

Parliament’s real power in UK treaty-making is typically seen as deriving from the need to pass any necessary implementing legislation.

The weak treaty role of the UK Parliament reflects the executive’s prerogative powers in international affairs. Protecting these seems to have been ministers’ main concern whenever the question has arisen in Parliament’s Brexit debates of what would happen if there were no Withdrawal Agreement. Protecting the prerogative will be the chief source of resistance to the “follow any direction” provisions in Lords amendment 19 today.

But the statute book includes instances in which Parliament’s role in treaty-making and UK international action has been varied from, or more exactly specified than, the default procedures.

For example, the European Union Act 2011 specified that the UK may not ratify a treaty amending or replacing the main EU Treaties unless the new treaty is approved by Act of Parliament; and it required passage of an Act of Parliament, or an approval motion (depending on the case), before the UK might take a number of actions at EU level, or consent to a slew of specific EU decisions.

As the House of Commons Library has pointed out, by giving the House of Commons a statutory veto over ratification of any Withdrawal Agreement either the Lords ‘meaningful vote’ amendment or its would-be government replacement would already represent a constitutional innovation.

The debate and votes on the ‘meaningful vote’ will thus represent only the latest instance in which Parliament’s role in international treaty-making is subject to a negotiation to fit particular circumstances.

And, with scope to shape Parliament’s role especially with respect to future international trade agreements and future agreements with the EU, apart from the more immediate Brexit considerations MPs should use the debate on the EU (Withdrawal) Bill amendments as an opportunity to think about the powers they want, at what point in the process, and with what time and information at their disposal.