>what is the citation for either the statute or regulation that sets forth the mandatory requirements for issuance of an executive order?
Trump 45 Admin already boxed them in and established that President Trump's social media posts are official presidential statements.
James Madison Project v. Department of Justice
Knight First Amendment Institute at Columbia University v. Trump
DOJ says Trump's tweets are official presidential statements
November 14, 2017
https://www.abajournal.com/news/article/government_says_trumps_tweets_are_official_presidential_statements