Her vetoing power, by refusing royal assent, is only permitted by law in the rarest of circumstances such as a constitutional crisis.
It is true that the Queen meticulously keeps up with the business of Parliament so that, in theory, if there ever were a constitutional crisis, she would be ready and properly advised to act, if necessary.
The Queen usually signs Letters Patent which allow the Speakers of the two Houses to announce the royal assent. However, she signs them for a whole lot of bills in one go, and is only given a list of the names of the Bills, not the texts or even the long titles.
She thus does not know the details of the Bills she is "assenting" to and is not expected to. That is because the process of assent, save in the rarest of situations such as a constitutional crisis, is now not much more than a ceremonial ritual.
The Queen is not even given a copy of the Bills and neither is the Palace. That is not just because she knows that both Houses of Parliament will already have considered the Bill very carefully but rather because she has no power to veto any of the Bills, save in constitutional emergency.
The proper constitutional authorities are the courts and Parliament and the authoritative text is Erskine May's Parliamentary Practice.
The procedure is set out here:
http://www.publications.parliament.uk/pa/ld/ldcomp/ldctso56.htm
and here
http://www.francisbennion.com/word/fb/1981/1981-011-royal-assent-procedure.doc
You will see that Francis Bennion describes the most common procedure (i.e. by notification under the Royal Assent Act 1967) at page 5 of 11. The Queen signs a general assent for a whole series of Bills at one time.
But says, Bennion:
"It is a striking illustration of the extent to which Royal Assent has become a mere formality that Her Majesty does not have before her the texts, or even the long titles, of the Bills to which she signifies assent. Indeed these are not even communicated to officials of the Queen's Household (colloquially known as the Palace)".
Bennion also confirms what is now the law:
"There is no power to withhold a Bill from Assent, whether on the instructions of the Government or anyone else.{See Erskine May Parliamentary Practice (19th edn.) p. 562: "from that sanction they cannot be legally withheld"}. Nor, under the modern constitutional convention, may the Queen refuse Assent. {The last time Assent was refused was by Queen Anne in 1707, in relation to a Scottish militia Bill (Lords' Journals (1705 1709) p.506).}...One of the strengths of Britain's unwritten constitution is the reserve power it contains. In a near revolutionary situation the occasion might still arise for the withholding of Royal Assent, if only by way of delaying tactics". [emphasis added]
Thus, in a dire emergency, the Queen's reserve power to refuse assent is permitted by law to save the Constitution and country and in a few other very rare situations, but not otherwise.
Professor Vernon Bogdanor's, The Monarchy and the Constitution, 1995, pp 131-132, gives an interesting insight into the discussions regarding the Home Rule Bill which King George V was very much opposed to:
"There is, then, no doubt that the king believed that he could veto legislation, and that he contemplated doing so in the case of Home Rule...the first parliamentary counsel, Sir Granville Ram...cited Dicey, who had declared of the refusal of assent: ‘Its repose may be the preservation of its existence, and its existence may be the means of saving the Constitution itself on an occasion worthy of bringing it forth’. The Home Rule crisis of 1914 proved that the sovereign retained the prerogative of veto, and that this prerogative might come into play on extreme occasions." [emphasis added]
The position adumbrated by Dicey is more or less the position today, as the authorities like Erskine May and Francis Bennion QC state.
We might call this "Dicey's exception".
was a leading constitutional lawyer
and Vinerian Professor of English Law at Oxford University from 1882 to 1909
Now, if the Queen were to refuse letters patent then she would be attempting to usurp to herself the power to veto a Bill - a power which the law and Constitution do not allow her.
And attempting to usurp or seize power unlawfully is a sin and we may not do evil that good may come of it, as St Paul teaches us (Rom 3:8), no matter how great the intended good may be.
It is not simply a matter of the Queen refusing to obey an unjust law. It is far more.
Any attempt by her to veto a Bill would be an attempted seizure of power by the Monarch, like the US President giving himself power to sack pro-abortion US Justices, a power he does not have under the US Constitution.
Once the US Senate confirms the nomination of a US Justice by an affirmative vote, the President must prepare and sign a commission, and have the Seal of the Department of Justice affixed to the document before the new justice can take office (see 5 USC § 2902).
The seniority of an Associate Justice is based on the date of commissioning, not the date of confirmation or swearing-in (see 28 USC § 4).
No-one would ever realistically suggest that the US President should refuse to sign the commission for any duly confirmed Justice, break the law, breach the Constitution which he is pledged to defend, and seize powers that he does not have (a coup d'etat), on the entirely spurious basis that he, the President, is morally compelled to do so in the name of over-turning Roe v Wade, the US Supreme Court decision that liberalised abortion law in the USA, and to stage a revolution in the name of the pro-life cause.
Revolution in the name of the pro-life, or any just, cause cannot be justified, and the whole weight of Catholic tradition and teaching on the subject is against it.
The position is summarised by St Thomas in De Regimine Principum, Ch. 6, 45-52, when he writes of the opinion that the unjust ruler may be overthrown by private force:
"But this opinion is not in accord with apostolic teaching, for Peter [1 Pet 2:18-19] admonishes us to be reverently subject to our masters, not only the good and gentle but also the froward...to proceed against the cruelty of tyrants is an action to be undertaken not through the private presumption of a few..."
In the British Constitution the true sovereign power lies with Parliament.
Even though the Queen is called the Sovereign, in truth, most of the time, she isn't, save for Dicey's exception.
To attempt to give herself the sovereign power to veto a Bill would be the act of a private citizen, Elizabeth Windsor-Mountbatten, attempting to seize power and overthrow the sovereign power of Parliament.
That would be the sin condemned by St Peter and St Thomas and one may not sin in order to achieve good, as St Paul teaches (Rom 3:8).
We should blame the real villains for the Abortion Act 1967: the politicians, not the Queen!
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