I dug deeper, and the use of the seal by Trump is definitely not authorized. As far as I can find, the Executive Order of 1976 is the last modification of the regulation. Notwithstanding the clear language and intent, an argument has been put forth that it is only criminal if it creates confusion.
"The statute regulating (not “barring” or “prohibiting”) use of the presidential seal is drafted with care. Under Section 713, one commits a crime only by displaying the seal “in a manner reasonably calculated to convey a false impression of sponsorship or approval by the government of the United States or by any department, agency, or instrumentality thereof.”
With due respect to Professor Carter, he makes too broad (and definitive) a claim, at least in this context, when he asserts "The federal statute is constitutional only so long as we read it to ban uses of the seal that are either deceptive or misleading, and nothing else. What the Trump Organization is doing, or what Amazon is doing, or what a publisher touting a book is doing, involves uses that are neither deceptive nor misleading."
First, his only reference is to dicta in a case about
another ordinance (in a county case). Second, it has to be placed in context: Trump continually, and falsely, asserts that he's still the rightful President, so his flogging of faux "official" materiel has a different character and, I would submit, falls clearly within the prohibition, to wit: displaying the seal “in a manner reasonably calculated to convey a false impression of sponsorship or approval by the government of the United States" Ergo, criminal use.