Apparently this is NOT true, because of a recognized legal principle called the "de facto officer doctrine".
According to the Supreme Court:
"The de facto officer doctrine confers validity upon acts performed by a person acting under the color of official title even though it is later discovered that the legality of that person's appointment or election to office is deficient."
- Ryder v. United States (94-431), 515 U.S. 177 (1995):
Good grief, wideminded, a thing like that would be harmless enough if it applied to dogcatchers; but as applied to an illegitimate POTUS, it's horrifically dangerous. This is like issuing a license to steal. Legal thinking like that does nothing to prevent a "fire-sale" of the United States of America.
You could put a rotten crook into office, and he can do stuff that cannot be undone. Regardless of whether he's punished after the fact, the damage is still there, and it is lasting damage.
Somehow I don't think this is what the Framers had in mind.
Thank you so very much for bringing Ryder v. United States (94431), 515 U.S. 177 (1995) to my attention!!!
This is what John Hemenway pointed out in the opening brief in Hollister v. Soetoro as it was posted here from Scribd. He asks why this Supreme Court precedent would not apply to Colonel Hollister as a member of the Individual Ready Reserve. If if the law is upheld and applied in that case it would seem to apply to Colonel Hollister and to many other members of the reserves as well. Colonel Hollister has challenged Soetoro a/k/a Obama as being only de facto and not de jure before he has been called back to active duty. That is why the Hollister case should now be the focus of a good deal of attention -- because of the Ryder case.