It was true until 2006. Now he can still run for president of France, but through the standard way : he can acquire French nationality through naturalization (like anyone) and run for president as a French citizen!
More precisely :
This article (Sorry, Bill Clinton. You can't be president of France or Ireland) explains deeply why :
Clinton likely got the Louisiana Purchase idea from political scientist Patrick Weil, who wrote an open letter to him in the New York Times in 2001 suggesting it:
Under Section 5 of Article 21-19 of the French civil code, citizens of states or territories over which France has ever exercised sovereignty or extended a mandate or protectorate may apply immediately for naturalization, without the normal five-year residency requirement.
Arkansas, where you were born, was once part of French Louisiana. And as a naturalized French citizen, you would have the same full rights as all other French citizens. That includes running for the presidency.
Unfortunately for Clinton, and his fellow Louisiana territory residents, Section 5 has been abrogé and doesn't appear in the current version of the code. According to a footnote in a 2004 New York Review of Books article, "After Weil's article made this provision of the French nationality law notorious, the French parliament abolished it in on July 24, 2006."
Here is the french civil code extract (Article 21-19):
Peut être naturalisé sans condition de stage :
5° Le ressortissant ou ancien ressortissant des territoires et des Etats sur lesquels la France a exercé soit la souveraineté, soit un protectorat, un mandat ou une tutelle ;