Article I, Section 8, Clause 10 of the U.S. Constitution authorizes the U.S. government to “define and punish Piracies and Felonies on the high Seas and Offences against the Law of Nations,” while Clause 11 authorizes the government to “declare War, grant Letters of Marque and Reprisal, and make Rules concerning captures on Land and Water.”

Any idea that unites Elon Musk and the authors of the U.S. Constitution, along with Donald Trump Jr. and Senator Mike Lee of Utah, to name but a few proponents, deserves at least a moment’s careful consideration. Senator Lee outlines his proposal in the following terms: 
Letters of Marque and Reprisal are government-issued commissions that authorize private citizens (privateers) to perform acts that would otherwise be considered piracy, like attacking enemy ships during wartime. Privateers are rewarded with a cut of the loot they bring home.
Going further, Lee notes that by issuing such letters, Congress could  authorize “private security firms or specially trained civilians” to “intercept cartel operations, particularly those involving drug shipments or human trafficking across borders.” Conceptually, at least, this idea dovetails interestingly with President Trump’s designation of cartels and other criminal organizations as terrorist organizations under the Alien Enemies Act.
So what are we to make of this? The notion of “privateering” goes back centuries, harking back to a time when navies were themselves often largely part-time endeavors, and authorizing armed merchant vessels to conduct acts of war represented a logical means of extending naval force. The inclusion of this capability in the U.S. Constitution reflected this, representing a means through which a young country, one with a very small navy but a very large merchant fleet, could assert its maritime interests more effectively.
But by the middle of the 19th Century, the major naval powers, the United Kingdom and France, no longer saw value in such irregular forces, ...