Justin Amash: Executive order limiting executive branch
Candidate for the Libertarian Party presidential nomination Rep. Justin Amash (L-MI), has stated on Twitter that his first executive order were he to be miraculously elected President of the United States would be to limit the powers of the executive branch to those explicitly found in the Constitution; clarifying in a later tweet exactly what practices would be banned under his hypothetical order.
The first problem with this order is that it's redundant; the Constitution already declares that all powers not explicitly granted to the U.S. government are not legitimate powers of the U.S. government and are reserved to the state governments or to the people themselves. It also reserves particular powers to the particular branches of the government, such as the power to declare war being a power of the legislative branch.
The second problem is that no current government can legally bind future governments because they have the same powers. Amash could issue such an order and follow it during his term, but the next president could revoke that order on their first day in office.
I don't know why Amash believes that an executive order would somehow have more force over what presidents can do than the Constitution itself, but there is no logical reason to believe that. As Lysander Spooner said, "But whether the Constitution really be one thing, or another, this much is certain—that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."
The Constitution has been ignored since the days of Washington, and we've only gotten further away from it in every regime since. That a document that is easier to ignore and/or repeal than the Constitution would do what the Constitution could not, that is: enforce itself, makes no sense.
Short of electing someone who actually takes what the Constitution says seriously as president, maybe that's Amash and maybe it's not, there is absolutely no hope in trying to stop politicians from centralizing power in the executive branch. This is what 200+ years of American history have taught us. Since the constituency for a federal government truly constrained by the Constitution is laughably small, the idea that we will ever actually elect such a person is, while not impossible, certainly out of the realm of probability.
I reached out to the Amash campaign to explain why this executive order would somehow have more force than the Constitution itself but received no reply. However, Dinesh D'Souza, God help me, made a similar point to mine on Twitter and did receive a reply from Amash.
Amash seems to be saying that his purpose for the executive order is merely to explain how his regime would operate in practice when in power, and does not seem to be making the argument that the executive order would be enforceable against future presidential regimes. He's making a political argument rather than a legal one, in short.
As I said previously, however, the American public does not want a strict constitutionalist as their president, and will not vote one into office anytime soon. Much less would they vote for a third-party candidate of no particular personal popularity. I still expect third-parties in general to do worse in 2020 than they did in 2016, but especially the Libertarian Party which had a record-setting year for themselves in 2016.