We are speaking purely theoretically, of course. However, I disagree. In principle a Constitutional amendment could not merely require that both parents be citizens but that they both be blond and over six feet tall and speak Latin. Although the Constitution itself says that there shall be no ex post facto laws, a Constitutional amendment would overturn that in regards to any specific point in the amendment.<quoted text>A constitutional amendment requiring two citizen parents would not be applied retroactively. It could not change the fact that BHO is in fact Prez.
What a Constitutional amendment cannot do, obviously, is rule that the tide not come in, or something physicl like that. But stupid human things, it can do and in fact has been done---for example, Prohibition.
But, as I said, Constitutional amendments are hugely difficult to pass. Still, if the birthers want to pass one---well,let them waste their time trying!