One of the most striking aspects of the arguments of counsel in Miller, as Rachel Jones has pointed out, was how much the disagreement between the parties focussed on the meaning of silence. The government’s case boiled down to an assertion that silence on the issue of whether legislation was needed to invoke Article 50 of the Treaty of European Union in a succession of statutes – the European Communities Act 1972, the Referendum Act 1975, the European Union (Amendment) Act 2008, the European Union Act 2011 and the European Union Referendum Act 2015 – should be interpreted as parliament intending that the government was permitted to use the prerogative to invoke Article 50. For example, counsel for the government repeatedly argued that because some of these statutes, especially the 2008 and 2011 Acts, put restrictions on the exercise of the government’s foreign affairs prerogative power, it must follow that those statutes mean that other aspects of the prerogative must have been intended to have been left unfettered. Expressio unius exclusio alterius. On the other side, the applicants argued that parliament’s silence, especially in the 1972 Act, meant that it intended a specific pre-existing rule to apply, namely the rule that ministers could not use the prerogative, and in particular the foreign affairs prerogative, to change the law. They also argued that parliament’s subsequent silence in the other statutes confirmed that original choice.

At one stage in oral argument, Lord Kerr asked counsel for the government whether its position was that parliament must either have intended the prerogative to encompass withdrawal from the EU or have intended to negative the existence of such a prerogative power and that it was impossible for parliament to have had no intention either way. James Eadie QC for the government conceded that parliament might not have decided either way, and that in those circumstances ‘you are thrown back on the nature of the prerogative power’. The task for the court is therefore more complicated than choosing between two competing rules. It is not simply to find what parliament has decided. It has to start with whether parliament has decided at all. As a result, it might be useful to think about the possible causes of parliament’s silence on an issue in a statute.

The first and most obvious cause of statutory silence is that no one thought about the issue at all. Governments usually have limited political objectives in putting forward bills and officials are understandably more interested in a bill’s intended consequences than in the full range of legal issues it might generate. The Office of Parliamentary Counsel (OPC) has responsibility for thinking through the legal consequences of bills, but it has limited capacity and often limited time. It cannot be expected to spot every possible future question. A law of diminishing returns soon sets in and ministers can quickly become impatient with drafting processes that take too long. Even less do backbench or opposition members of parliament have sufficient time and resources to spot issues that might have escaped the government. They too normally focus their attention on the political effects of the bill.

A second possible cause of statutory silence might be called the can of worms situation. The government might realise, either from the outset or after analysis by OPC, that an issue will arise but decide that the difficulties of resolving it are so great that it would be better not to mention it. Those difficulties might be technical, in the sense that the legal or practical consequences of deciding the issue one way or the other might be impossible to calculate, or they might be political, in the sense that any attempt at resolution would bring into the debate, or bring back into the debate, issues that divide the governing party. Occasionally the latter can happen on the opposition side. Opposition parliamentarians might notice a problem not addressed by the bill but judge that it raises more political difficulties for the opposition than it does for the government.

A third possible cause of statutory silence is that government and parliament have made a conscious determination that the solution to the problem already exists in an existing legal rule. If that legal rule is to be found in another statute or in case law (what we will call from now on an ‘external rule’), it does not need to appear in the bill itself. As a consequence, the bill might well remain silent on the issue. This is the situation contended for by both sides in Miller, albeit for opposing external rules.

A fourth possible cause of statutory silence is that government or parliament, or both, realise that an issue exists and are uncertain how the courts would resolve the point. Instead of proposing a solution, however, perhaps because of the difficulty of the issue or because they lack sufficient information, they consciously decide to leave the point to be determined by the courts. The situation might look the same as the can of worms situation, since in both the decision falls back onto the courts, but the difference is that in the former it would still be possible for the court to conclude that the issue was not justiciable, whereas in the latter parliament specifically intends the issue to be justiciable.

These possible causes of statutory silence have very different legal implications. Silence caused by complete inadvertence – that the problem was not anticipated at all – has no interpretive consequences. Nothing comes from nothing. The can of worms situation is slightly different. The government, and perhaps parliament, knows a problem exists but opts for none of the solutions available at the time. Does that mean one can infer that the government or parliament must have supported the status quo, whatever it was? Not really. For one thing, one cannot assume that the government or parliament knew, or even thought it knew, what the status quo was. The reason for not opening a can of worms is that one doesn’t know what might wriggle out if one opens it. As for supporting the status quo, the essence of the can of worms situation is that the status quo is unsatisfactory precisely because it is uncertain. To infer support for a specific rule in these circumstances is implausible. In contrast, in the third situation the government, or parliament, has identified an applicable rule. As long as one can say what that rule is, it is more than plausible to say that parliament intends that it should apply. In the fourth situation parliament again has no intention as to the substantive solution to the problem but it does have an intention about who is to find and take responsibility for a solution, namely judges.

And so how can we tell the difference between these four situations? The central problem is how to distinguish the first and second situations, which have no interpretive consequences, from the third and fourth, which have consequences, albeit of different kinds.

An obvious point is that the first and second causes leave no trace – the first by definition and the second by design. But absence of evidence is not evidence of absence. We cannot say as a matter of pure logic that if we have no evidence of support for an external rule there could have been no support for such a rule. It is perfectly possible for a mental state to have existed but for no evidence of that state ever to have been created. On the other hand, government has a number of opportunities to reveal its thoughts, including green and white papers, other kinds of consultation documents, impact statements and explanatory notes on bills, without even mentioning the more controversial materials of ministerial statements to parliament and speeches on bills at various stages of the legislative process (controversial because of MP’s anxieties about the prospect of litigation might change the content of their speeches and thus give rise to infringements of Article 9 of the Bill of Rights 1689). Traces of such decisions might also crop up in research commissioned by government departments or even in academic research or research carried out by the House of Commons’ or Lords’ Libraries. If the government takes none of those opportunities, it seems unlikely that it had a specific external rule in mind. At the very least, it cannot reasonably object if outsiders conclude that it has not landed on a specific external rule. If relevant amendments are offered and rejected one can certainly conclude that we are not in situation 1, complete inadvertence, but we might still be in situation 2, the can of worms, or in situation 4, delegation to the judges. On the other hand, if an amendment is rejected expressly on the ground that the amendment is unnecessary in the light of a specific rule from outside the bill, one can reasonably infer an intention to adopt that rule despite the bill’s own silence on the issue. But if one cannot say with certainty which external rule is intended, if, for example, one could equally plausibly say that the exact opposite rule was the right one, we are not in situation 3.

Telling the difference between situation 2, the can of worms, and situation 4, delegation to the judges, can be done in a similar manner. An intention to delegate to the judges would be evidenced by ministerial statements to that effect – for example in a white paper or a consultation document or by a minister saying in debate that an issue ‘should be left to the courts’ or is a ‘matter for the courts’ (this often happens on issues of sentencing or remedy, see eg the committee stage debate on the Bribery Bill in 2010 , the committee stage of the Crime and Disorder Bill in 1998 and the committee stage of the Criminal Justice and Police Bill in 2001). It is possible for an intention to delegate to be formed without leaving any evidence but enough opportunities exist to provide such evidence that its absence can reasonably be taken as significant.

Applying the forgoing analysis to Miller, the simplest summary of the argument of counsel on all sides is that no one has found any trace in white papers, green papers, consultation documents, impact assessments or in Hansard of any decision in the 1972 Act or any of its successors to adopt a specific rule either way about whether ministers have a prerogative power to invoke Article 50 TEU or even evidence of a conscious decision to delegate the issue to the courts. As between inadvertence and cans of worms, the evidence is inconclusive. Certainly parliament was conscious, at least in 1972, of issues surrounding possible withdrawal (see for example the debate on Sir Elwyn Jones’ sovereignty amendment, an amendment rejected by the government on the mixed and so in itself uninformative ground that its first part was unnecessary and its second part incompatible with joining the EEC) but debate focussed on whether withdrawal was possible at all and what the consequences would be of the United Kingdom breaching its obligations in international law. No one talked about the mechanisms of withdrawal. Counsel in Miller did find the gnomic statement by Gerry Fowler, the minister in charge of the Referendum Bill 1975, that the referendum would ‘not be binding on Parliament, although it is binding on the Government’, a statement he expanded in committee, in inviting the committee to reject an amendment as unnecessary, with the declaration ‘It is not for the House to attempt to bind, through legislation, the Government’s attitude to the result of the referendum. That is a matter for the individual or collective decision of my right hon. and hon. Friends. Equally, the result of the referendum, however high the turn out, cannot bind the House in a meaningful way.’ Since both sides in Miller agreed that parliament is perfectly entitled to restrict prerogative powers if it wants to, whatever Mr Fowler had in mind in this statement it could not have been anything to do with the issue before the court.  The nearest one can get to awareness of the issue is the point raised by James Eadie QC for the government that the 2008 Act and the 2011 Act deal with closely related issues, such as prohibiting the use of the foreign affairs prerogative in the Council of the European Union to expand the powers of the EU, and Lord Carnwath pointed out that those provisions mention Article 50(3) TEU, under which member states remaining in the EU have various voting rights in the Council. Mr Eadie ran the argument that awareness of the issue demonstrates an intention not to restrict the government’s prerogative. That argument does not work, because in the absence of specific reference to an external rule the can of worms explanation is better. But it is not even absolutely clear that these references rule out inadvertence. The government was possibly searching the Treaty for references to member state voting rights in the Council of the European Union, which it could easily have done without noticing other issues in the Treaty articles that search reveals.

It seems to follow, as Mr Eadie presaged and perhaps feared, that the result in Miller should depend not on attributing meanings to parliamentary silence but on the nature and scope of the prerogative power itself.

David Howarth, Professor of Law and Public Policy, University of Cambridge

(Suggested citation: D. Howarth, ‘On Parliamentary Silence’, U.K. Const. L. Blog (13th Dec 2016) (available at https://ukconstitutionallaw.org/))