Article 2, Section 2, Clauses 2 and 3
William Blackstone, Commentaries 1:245--47, 2491765
With regard to foreign concerns, the king is the delegate or representative of his people. It is impossible that the individuals of a state, in their collective capacity, can transact the affairs of that state with another community equally numerous as themselves. Unanimity must be wanting to their measures, and strength to the execution of their counsels. In the king therefore, as in a center, all the rays of his people are united, and form by that union a consistency, splendor, and power, that make him feared and respected by foreign potentates; who would scruple to enter into any engagements, that must afterwards be revised and ratified by a popular assembly. What is done by the royal authority, with regard to foreign powers, is the act of the whole nation: what is done without the king's concurrence is the act only of private men. And so far is this point carried by our law, that it hath been held, that should all the subjects of England make war with a king in league with the king of England, without the royal assent, such war is no breach of the league. And, by the statute 2 Hen. V. c. 6. any subject committing acts of hostility upon any nation in league with the king, was declared to be guilty of high treason: and, though that act was repealed by the statute 20 Hen. VI. c. 11. so far as relates to the making this offence high treason, yet still it remains a very great offence against the law of nations, and punishable by our laws, either capitally or otherwise, according to the circumstances of the case.
I. The king therefore, considered as the representative of his people, has the sole power of sending embassadors to foreign states, and receiving embassadors at home. This may lead us into a short enquiry, how far the municipal laws of England intermeddle with or protect the rights of these messengers from one potentate to another, whom we call embassadors.
The rights, the powers, the duties, and the privileges of embassadors are determined by the law of nature and nations, and not by any municipal constitutions. For, as they represent the persons of their respective masters, who owe no subjection to any laws but those of their own country, their actions are not subject to the control of the private law of that state, wherein they are appointed to reside. He that is subject to the coercion of laws is necessarily dependent on that power by whom those laws were made: but an embassador ought to be independent of every power, except that by which he is sent; and of consequence ought not to be subject to the mere municipal laws of that nation, wherein he is to exercise his functions. If he grossly offends, or makes an ill use of his character, he may be sent home and accused before his master; who is bound either to do justice upon him, or avow himself the accomplice of his crimes. But there is great dispute among the writers on the laws of nations, whether this exemption of embassadors extends to all crimes, as well natural as positive; or whether it only extends to such as are mala prohibita, as coining, and not to those that are mala in se, as murder. Our law seems to have formerly taken in the restriction, as well as the general exemption. For it has been held, both by our common lawyers and civilians, that an embassador is privileged by the law of nature and nations; and yet, if he commits any offence against the law of reason and nature, he shall lose his privilege: and that therefore, if an embassador conspires the death of the king in whose land he is, he may be condemned and executed for treason; but if he commits any other species of treason, it is otherwise, and he must be sent to his own kingdom. And these positions seem to be built upon good appearance of reason.For since, as we have formerly shewn, all municipal laws act in subordination to the primary law of nature, and, where they annex a punishment to natural crimes, are only declaratory of and auxiliary to that law; therefore to this natural, universal rule of justice embassadors, as well as other men, are subject in all countries; and of consequence it is reasonable that wherever they transgress it, there they shall be liable to make atonement. But, however these principles might formerly obtain, the general practice of Europe seems now to have adopted the sentiments of the learned Grotius, that the security of embassadors is of more importance than the punishment of a particular crime. And therefore few, if any, examples have happened within a century past, where an embassador has been punished for any offence, however atrocious in it's nature.
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II. It is also the king's prerogative to make treaties, leagues, and alliances with foreign states and princes. For it is by the law of nations essential to the goodness of a league, that it be made by the sovereign power; and then it is binding upon the whole community: and in England the sovereign power, quoad hoc, is vested in the person of the king. Whatever contracts therefore he engages in, no other power in the kingdom can legally delay, resist, or annual. And yet, lest this plenitude of authority should be abused to the detriment of the public, the constitution (as was hinted before) hath here interposed a check, by the means of parliamentary impeachment, for the punishment of such ministers as advise or conclude any treaty, which shall afterwards be judged to derogate from the honour and interest of the nation.
The Founders' Constitution
Volume 4, Article 2, Section 2, Clauses 2 and 3, Document 2
The University of Chicago Press
Blackstone, William. Commentaries on the Laws of England: A Facsimile of the First Edition of 1765--1769. Chicago: University of Chicago Press, 1979.