The UK House of Commons has just seized control of Brexit. So what happens next?

Simon Usherwood is Professor of Politics at the University of Surrey, and Dep Director of the "UK in a Changing Europe".

This week, the British Parliament decided to take Brexit into its own hands. On Monday night, they accepted an amendment that means they will now spend the coming days taking a series of indicative votes – essentially, votes to test the extent of support for a number of options that the United Kingdom could follow in its slow and painful withdrawal from the European Union.

This decision by Members of Parliament is significant because it is the first time that they have pushed back against the government of Theresa May in a way that might fundamentally change the path of Brexit. Yes, MPs did vote (twice) against the deal that May had brought back from her negotiations with the EU, but on both occasions, they effectively left it up to her to work out the next steps.

By contrast, the indicative votes have the potential to force choices on the government. But this is not without its difficulties.

Voting on what?

Firstly, Parliament has to decide what those choices might be. It’s one thing to say that it doesn’t like the current Withdrawal Agreement, but quite another to map out the alternatives.

In practice, these break down into two main categories: options on outcome and options on procedure.

The current deal says that the UK and EU will work towards an extensive free trade agreement, but with the UK outside of the EU’s single market and customs union. These imply a relatively distant relationship – the single market and customs union are at the heart of the EU’s economic integration. So Parliament will want to consider whether committing to staying within either or both of these is preferable.

Those options are consistent with what the EU might be willing to negotiate in a future relationship after membership, but Parliament has also seen other ideas that are much less acceptable. These include the Malthouse Compromise and the Brady amendment, both of which seek – among other things – to renegotiate the Irish backstop element of the Withdrawal Agreement, something that the Europeans have ruled out doing.

Procedurally, the big question facing Parliament is whether to throw the matter back to the electorate with another referendum. While this lacks a large degree of support among MPs at present, it might look more appealing if those MPs decide they want to pursue a course of action that is very different from the one undertaken so far by the government.

At the most basic level, the choice of options that MPs will select from is likely to be a very political process, so it will need to be seen to be fair if it is to produce a useful conclusion.

Voting how?

That need for fairness extends to the second major problem: How to select among the options?

Parliament does not have much experience in these kinds of votes and the last major attempt – on House of Lords reform back in the late 1990s – produced an outcome where no one option got majority support.

Here the choice for MPs is whether to simply gauge their views or to force them towards more of a consensus.

It is quite simple to produce a list of options and then to ask MPs to indicate which is their preferred one. But if there’s one thing that has been clear in recent months it is that there is no course of action that a majority supports. The only exception to this is a strong desire to avoid leaving without a deal, but that is not sufficient by itself to guide what happens instead.

What seems likely then is some system of ranking or preferential voting, possibly done in several rounds, to knock out the least-popular options and to try and build more support for alternatives. This makes sense in trying to get a more determined answer from MPs, but it also underlines how important it is that there is an appropriate selection of options for them to choose from.

To take just one (very possible) scenario, it may be that there is a majority for some second-best option that has hardly any support as a first choice. If MPs haven’t been asked about their ordering of preferences, then that second-best compromise might have been knocked out of the running before it can emerge.

By the same token, voting systems contain the potential to produce perverse outcomes. The authors of the process that will be used must be aware of the biases and incentives that will be present and clear to MPs about how the process itself will shape the outcome.

Voting for what purpose?

The final challenge facing Parliament on these votes will be the extent to which the government takes any notice of the outcome.

Theresa May already indicated on Monday that she would not be willing to follow instructions that went against her party’s election manifesto; that is she will reject any plan to maintain membership in the single market or customs union. Since the government controls the very large part of the Commons’ business, MPs might find that they have spent much effort on something that is effectively ignored.

In that situation, the big question will be whether MPs take a further step to shape matters by changing their rules – the ones that currently give the government so much power – to produce new decisions that compel May and her ministers to follow the will of Parliament. That would be a big step for a body that has long been relatively weak in asserting its powers, but would bring it more in line with equivalents in other countries.

Of course, such actions would not be without consequences.

In the context of Brexit, the EU might find it hard to know whether the government or Parliament is now in charge of negotiations, with all the issues that this might produce. If there is a lasting stand-off between different parts of the UK system how is the EU going to be able to plot a course that both reaches a stable outcome and that protects its own interests? In the face of such uncertainty, the EU might feel it is better just to walk away from more confusion and instability.

Domestically, such a move would underline just how weak the current government has become.

For some MPs, that might just be the push they need towards deciding that the time has come to call it a day and to allow a general election to take place. And how that would turn out is even more uncertain and problematic than these indicative votes, especially given the depth of feeling on all sides about this process. Given that both the Conservatives and Labour lack clear policies on Brexit, even a general election might not resolve the issue in a lasting way.

Just as the UK is finding Brexit difficult to get a handle on, so too might Parliament find that there are no easy answers.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.