If I somehow mean Obama, I'm addressing him as Mr president until he tells me otherwise. Bill clinton is on record as preferring just "Mr Clinton".

But it's not appropriate in the 3rd person. The media gets it wrong when they say things like "the president is now entering the courthouse." That would be the *former* president. Or better yet, the disgraced, lying, raping, defaming, fraudulent, confidential information stealing, failed businessman who briefly cheated his way into the Oval Office once.

Fixed, thanks!

is incorrect. The original Miss Manners was also chief of protocol in the US govt in the 1960s. I don’t know who would be a more reliable authority on this.

The rationale is that, because there is only one President at a given time, s/he is the only one who should be addressed by that title. In contrast, there are multiple Senators, Governors, etc., at a given time, so there is no confusion or disrespect, if we also address a former office holder by that title.

One can find their statements about this online. For example:

https://www.uexpress.com/life/miss-manners/2003/12/02

the correct form is “Mr. LastName.” (“President LastName” or “Mr. President” are terms reserved for the current head of state.) This is true for other ex-officials, as well. When talking about the person to a third party, on the other hand, it’s appropriate to say, “former President LastName.” This holds for introductions, as well: A current state governor is introduced as “Governor Tom Smith,” while you’d introduce an ex-governor as “former Governor Jim Bell.” https://emilypost.com/advice/addressing-a-former-president-of-the-united-states#:~:text=When%20addressing%20a%20former%20President,ex%2Dofficials%2C%20as%20well.

I DON'T CARE HOW THEY ADDRESS HIM!
They can sew a big Presidential Seal on his prison uniform!!
I'll be dancing in the streets!