From the abstract for Julian Davis Mortenson, Article II Vests Executive Power, Not the Royal Prerogative, Columbia Law Review, Forthcoming:
Article II of the United States Constitution vests “the executive power” in the President. For more than two hundred years, advocates of presidential power have claimed that this phrase was originally understood to include a bundle of national security and foreign affairs authorities. Their efforts have been highly successful: among constitutional originalists, this so-called Vesting Clause Thesis is now conventional wisdom. But it is also demonstrably wrong.
Based on an exhaustive review of the eighteenth-century bookshelf, this article shows that the ordinary meaning of “executive power” referred unambiguously to a single, discrete, and potent authority: the power to execute law. This enforcement role was constitutionally crucial. Substantively, however, it extended only to the implementation of legal norms created by some other authority. It wasn’t just that the executive power was subject to legislative influence in a crude political sense; rather, the power was conceptually an empty vessel until there were laws or instructions that needed executing.
There was indeed a term of art for the Crown’s non-statutory powers, including its various national security and foreign affairs authorities. But as a matter of well-established legal semantics, that term was “prerogative.” The other elements of prerogative—including those relating to national security and foreign affairs— were possessed in addition to “the executive power” rather than as part of it.