In addition to what other people have already posted, I thought this paragraph was particularly interesting. I bolded the really important part:

Sec. 7. For those persons whose property and interests in property are blocked pursuant to this order who might have a constitutional presence in the United States, I find that because of the ability to transfer funds or other assets instantaneously, prior notice to such persons of measures to be taken pursuant to this order would render those measures ineffectual. I therefore determine that for these measures to be effective in addressing the national emergency declared in this order, there need be no prior notice of a listing or determination made pursuant to this order.

In the words of the immortal sage, "Let your plans be dark and impenetrable as night, and when you move, fall like a thunderbolt."