He's not just any private citizen, he's the president elect who will be inaugurated in a day. I'm sure his word carries way more weight than mine.
I'm not privy to the specific words that were exchanged, so it's hard to be precise. But I imagine it was some form of Trump saying "by tomorrow, I will give you a 90-day extension. I have a gentleman's agreement with the current government that if you do not stop your services in the 24 hours between now and my inauguration, you won't face any issues, so please carry on and we will clean this mess up later".
If you want a private citizen analogy, it's similar to someone saying they won't press charges despite a third-party being in flagrant illegal behavior. In this case, it's the US government saying they won't press charges. Both Biden and Trump have said as much, if my understanding of the case is correct, and one can assume they have discussed this with the appropriate branches of government.
Trump does not have the authority to give a 90 day extension by the language in the law from my understanding. There was a provision for a single use 90 day extension that would require the president to certify 3 things (which currently has not been met and can not be met within days) and have that delivered to congress prior to the ban taking affect. The law gives no mechanism to provide an extension after the ban according to republican legislators.
He must simply _claim_ that the 3 requirements have been met according to his own interpretation of the facts on the ground. It doesn't mean that his interpretation must be correct; He has the discretion to provide the extension per the law.
If someone challenges his interpretation of the 3 requirements in court, then presumably he'd have to explain why he believed that to be the case[1], but he does not have to prove this certainty ex ante in order for the 90-day extension to be valid.
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[1]: IANAL but whether he can successfully prove it or not is also ultimately irrelevant given the SCOTUS recent interpretation of presidential power. If he's found "guilty" of making a bad interpretation of the certainty of the 3 requirements, what is really going to be his punishment? There's really nothing you can do against a sitting president with regards to the exercise of their executive power...
He does not need to simply _claim_, he must certify. And one of those is:
“there are in place the relevant binding legal agreements to enable execution of such qualified divestiture during the period of such extension."
This is a binary thing. No such legal agreement seems to exist. You also ignored the other parts of my comment about him missing the deadline in the law to apply the extension.
"Certify" does not mean the same as prove with evidence. I don't think there's a specific threshold that has to be met there other than the parties agreeing it has been certified. It can even come down to as much as "trust me bro" from the president.
The definition of certify is literally "attest or confirm in a formal statement"
Besides, there's no process through which Congress would question or investigate whether the president really can or cannot certify whatever he claims about this matter.
I'm not privy to the specific words that were exchanged, so it's hard to be precise. But I imagine it was some form of Trump saying "by tomorrow, I will give you a 90-day extension. I have a gentleman's agreement with the current government that if you do not stop your services in the 24 hours between now and my inauguration, you won't face any issues, so please carry on and we will clean this mess up later".
If you want a private citizen analogy, it's similar to someone saying they won't press charges despite a third-party being in flagrant illegal behavior. In this case, it's the US government saying they won't press charges. Both Biden and Trump have said as much, if my understanding of the case is correct, and one can assume they have discussed this with the appropriate branches of government.