Queen Elizabeth II was generally nice and didn't abuse her power. But could her successor do otherwise and "go full dictator", in theory? Would he have enough legal powers to do so? Admittedly, dictators are not known for playing by the book, but they often start out in a lawful or a "semi-lawful" fashion. To what extent, if I put it another way, does the British democracy rely on solid legal checks and balances, not on the monarch's goodwill? Considering the UK's uncodified constitution, which is not really there, one may start to have some doubts about it.
Parliamentary Supremacy was established by the Glorious Revolution of 1688 in which James II & VII was deposed by Parliament, and the line of succession was changed by Act of Parliament to favor William and Mary.
Key laws passed during the aftermath of the Revolution included the Declaration of Right (which forbade keeping a standing army without Parliamentary consent, and put control of the military in Parliament), and the Coronation Oath Act 1688 which established in law obligations of the monarch.
Since 1688 it has remained the governing principle of English (later British and UK) law that ultimate authority lies in Parliament, not with the monarch, and that Parliament can at any time depose a monarch for failing to act properly, and can settle the line of succession to the crown.
A British King or Queen who tried to exercise dictatorial power, or even to use remaining Royal Prerogative powers to assume personal rule, could and quite likely would be deposed.
Most of the Royal Prerogative powers are today exercised by the politicians in government, not by the monarch. That is partly a matter of the goodwill of the monarch, but mainly a cultural fact that has developed over centuries. That is something both well established (as norms are) but also not on completely sound footing. Norms often seem inviolable until they are violated - see the behaviour of (so-called) "populist" governments in various countries in recent years.
Of course, a constitutional monarch abusing norms is probably harder than an elected politician doing so, but it can still happen. Perhaps the most famous example of the monarchy breaking the 'don't interfere in politics' norm was the 1975 Australian constitutional crisis. The British Cabinet Manual notes that the last time something like that happened in the UK was in 1834 under William IV, when he deposed Lord Melbourne as Prime Minister.
But let's say you have a monarch willing to break these established norms and Parliament/the citizenry are too meek to immediately reassert their authority. What could a monarch actually do with the Royal Prerogative, legally speaking?
Probably the most important legal case that examined the Royal Prerogative was Council of Civil Service Unions v Minister for the Civil Service, where the Thatcher government tried to prevent GCHQ employees from being members of trade unions (purportedly for reasons of national security).
The judges found for the government, but in particular ruled that questions of the exercise of the Royal Prerogative are nevertheless judiciable. So in principle, judges can examine how the Royal Prerogative is used (whether by the monarch themselves, or more usually, by politicians in their name).
More generally, whilst Parliamentary Sovereignty has wide berth, judges have on occasion been known to hint that even it has some limits. Most famously, in R (Jackson) v Attorney General, a case related to (of all things) fox hunting, Lord Steyn opined:
If that is so, it is not unthinkable that circumstances could arise where the courts may have to qualify a principle established on a different hypothesis of constitutionalism. In exceptional circumstances involving an attempt to abolish judicial review or the ordinary role of the courts, the Appellate Committee of the House of Lords or a new Supreme Court may have to consider whether this is a constitutional fundamental which even a sovereign Parliament acting at the behest of a complaisant House of Commons cannot abolish.
As such, there is a significant body of academic opinion (though perhaps only a minority?) that believes both executive and legislature in the UK are, in theory at the most fundamental level, limited by the judiciary using modern democratic and human rights doctrines, even if in only the most extreme cases.
And it's easy to see how these sorts of ideas could also be applied to a monarch acting more assertively than now. But naturally, in practice this comes down to who the judges are and their philosophical convictions, not any certainty.
As an example, consider the case of the Chagossians. For those who don't know, the Chagos Islands is an archipelago in the Indian Ocean, controlled by Britain as a remnant of the British Empire. In the late 60s and early 70s, the native population of the islands were forcibly expelled, in order to make way for a US military base that remains there to this day.
In 2000, the British courts ruled that the Chagossians should be allowed to return to their homeland. However, in 2004, the Blair government used Royal Prerogative powers to overturn the earlier decision, and prevent any return. A number of legal cases since have examined that use of the Royal Prerogative and, long story short, have said that although the question is judiciable, ultimately it was a perfectly legal use of the Royal Prerogative powers.
Now, on the one hand, this sort of ruling is hard to generalize, given the nature of colonialism as allowing a State to create exceptions for how it treats colonial subjects versus how it treats people in the metropole.
But on the other hand, consider what this means in the abstract: in theory an autocratic British government could commit illegal acts (as dictators are wont to do), and when a court finds against the dictator and orders their actions be remedied, the government can simply use the Royal Prerogative to overturn the court's decision and carry on with their abusive regime.
And this is before you even notice that under international law, the UK is not recognised as sovereign over the Chagos Islands, and has been ordered by the ICJ and UN General Assembly to hand over the territory so as to complete the decolonisation of Mauritius!
At a certain point, this sort of question reaches a legal black hole based on 1) the nebulous nature of the UK's mostly uncodified constitution, 2) the clash between national and international law, and 3) the ultimate ontological root origin of law as a sociological construct that cannot guarantee its own certainty.
The Queen COULD have refused to ask Liz Truss to form a government last week. She COULD withhold Royal Assent to a bill that Parliament presented to her. She doesn't (didn't, RIP) do such things. The legal position if she tried is unclear (as it was over the unusual proroguing of Parliament before 'getting Brexit done').
The chances of Charles III trying it are about as remote as those of an American president refusing to hand over power to his elected successor.
And that wasn't just a mischievous comment. When popular feeling runs high, power can become de facto rather than de jure. Legal constraints become irrelevant, it's not impossible that the British public might rally behind King Charles in revolution against their corrupt government! I don't think we need to become paranoid Preppers just yet though.
The Sovereign has no real power
Power in the UK (and Canada, Australia, New Zealand etc) rests with Parliament.
This has been the case since the Bill of Rights of 1689.
While the sovereign has some powers, they have (with the exception of inconsequential Royal Prerogatives) no discretion in how to apply them. For example, the sovereign must give Royal Assent to a Bill passed by Parliament - the power seems discretionary, but it isn't.
What would probably happen then is that the supreme court would find they violated the Bill of Rights suspend their judgement, and then parliament would vote to remove the monarchy. The Bill of Rights states this, among other things.
the pretended power of suspending the laws and dispensing with laws by regal authority without consent of Parliament is illegal
There's no easy legal route for them to take over.
I shall focus on Royal Assent. First, I quote Maurice Sunkin's Public Law Text Cases Materials (4th edn, 2019), page 34.
Withholding Royal Assent (for example, because the Queen had a moral objection to something in the bill) would be undemocratic. Conclusion: there is a convention.31
31 Matters may be somewhat more complicated. If you want to delve deeper, see N.W. Barber, ‘Can Royal Assent Be Refused on the Advice of the Prime Minister?’, UK Constitutional Law Blog, 25 September 2013, http:// ukconstitutionallaw.org.
I quote Keith Ewing, Constitutional and Administrative Law (18th edn, 2022), pages 21-2.
The monarch’s legal power to refuse Assent was last exercised by Queen Anne in 1708, when (apparently with the approval of her ministers and without objection by Parliament) Assent was refused to the Scottish Militia Bill.120 In the Irish crisis of 1912–14, the Unionists suggested to George V that he should withhold Assent from the Bill to give home rule to Ireland. The Liberal Prime Minister, Asquith, advised the King against this and the Royal Assent was granted.121 While the Queen may not of her own initiative refuse the Royal Assent, the position might be different if ministers advised her to do so, although this advice would have to be defended in Parliament and, depending on the circumstances, could be highly controversial. 122
120 Hearn, The Government of England, p 61.
121 Jennings, Cabinet Government, pp 395–400. Cf Brazier, Constitutional Practice, pp 193–6. See too: Twomey, The Veiled Sceptre.
122 The highly acclaimed 2014 play by Mike Bartlett, Charles III, has as its premise King Charles III exercising his refusal of Assent to a Bill limiting press freedom, with significant consequences. A real-world example arose in the fraught process of negotiations with the EU over withdrawal, when Parliament twice passed primary legislation obliging the Government to seek an extension of membership which it did not wish to seek (see ch 6). Could the Prime Minister constitutionally have advised the Queen to refuse the Royal Assent to such Bills? It is well arguable that such advice could have been given, although whether the Queen was then bound to accept that advice – contrary as it would have been to the expressed wishes of both Houses of Parliament – is a further vexed question. The obvious and considerable constitutional ramifications of such steps have usually caused politicians to avoid such questions having to be asked, and it is a testament to the political tensions over Brexit that they were more seriously considered than at any time in recent history.
Two people were arrested for holding signs questioning the existence of the British Monarchy in London this week.
The NRLW athlete Caitlin Moran was suspended for criticizing the queen on social media.
There are hundreds of pictures and videos on social media showing pictures mourning the queen everywhere in England nowadays, kinda forcing you to mourn her.
If that's not a dictatorship, I don't know what it is.