Illustration by Eva Bee

One of the golden rules of politics is that if your opponent is attacking you personally then they are rattled.

As we now see with the Brexit debate, those who are wildly enthusiastic about the UK leaving the EU are focused on knocking out any dissenting voices rather than actually answering the hard constitutional and practical questions that have arisen as a consequence of the 23 June vote.

Their tactics have even reached the high court, with the court taking a dim view of the abuse suffered by lead claimant Gina Miller, the other applicants and their counsel in the current article 50 case.

This battle for parliamentary sovereignty over the steps needed to carry out Brexit really matters for a number of reasons. First, we know that the trigger to start the formal Brexit negotiations is to serve a notice under article 50 of the Lisbon treaty. As is made clear in the current court case, once that notification has been served it means the UK will be leaving the EU – there is no provision for a conditional notice to be served nor for notice, once given, to be withdrawn.

Second, the EU Referendum Act 2015 made no provision for what happens in the event of a yes vote, unlike the Parliamentary Voting System and Constituencies Act 2011. The 2011 act set out what the relevant minister must do in the event of a yes vote.

Third, in 2010 – in response to the observation from the House of Lords select committee on the constitution that referendums cannot be legally binding in the UK because of the sovereignty of parliament – the previous government expressly said: “Under the UK’s constitutional arrangements parliament must be responsible for deciding whether or not to take action in response to a referendum result.”

That select committee, with cross-party and crossbench representation, also observed that although referendums cannot be legally binding, “It would be difficult for parliament to ignore a decisive expression of public opinion.” I agree with that. But I think that in the event of any Brexit vote, MPs on all sides will be extremely aware of how their constituents voted in June.

Finally, as Stephen Phillips, leave voter and Conservative MP for Sleaford and North Hykeham, has said, it would be strange to have voted to regain our sovereignty in the UK to then see our sovereign parliament not heavily involved in a matter of such constitutional importance as our future relationships with other European nation states and the European Union.

For these reasons, many of us in parliament, in line with the argument put forward by the applicants to the high court, strongly believe that parliament should be asked to formally approve the serving of a notice under article 50, given the serious and irrevocable consequences of doing so.

MPs are also expecting, although there seems to be some confusion here, that either a white paper or some other kind of document will be put before them setting out the broad negotiating stance the UK government intends to take in its discussions with the EU.

It would also tell us what future relationships ministers are aiming for – including on the issues that the prime minister was clearly worried about before the Brexit vote, as her remarks to Goldman Sachs, first revealed by the Guardian, demonstrate. The idea of a white paper was first floated by the Brexit secretary just before his cabinet appointment and he was right to do so.

Why does it matter, some may ask, that parliament is involved in the UK’s exit from the EU? Why not just leave it to the government to use its executive power? After all, we know that in recent years governments have agreed not to declare war or commit our troops to overseas engagements without parliamentary scrutiny and approval.

Commons votes were held in 2011 on our involvement in Libya, in 2013 and 2015 on involvement in the Syria conflict and against Islamic State in Iraq. I would argue that in terms of our country’s international profile, Brexit is just as significant a development as any military engagement.

Parliamentary sovereignty – the right to pass laws as the supreme legal authority in the land, including laws that limit the powers of the executive – has been hard-won over hundreds of years. We trample on it at our peril. It may be Brexit now, but what next? Who is to say what element of our constitution could be questioned in future?