From Paris to Tsuri,
WWII started 1939, September 2nd.
Phoney war ended in May 1940 when Hitler invaded Belgium, Nederlands then France (Blitzkrieg, May 10th - June 14th).
On June 14th, Nazis entered Paris.
This was an end to the Republican and democratic state and Petain obtained full power from Parliament.
As soon as July 22nd, an antisemitic law had been passed to "de-naturalize" foreign Jews who had been naturalized by 1927 law.
This law gave an easy access to French citizenship, a way to repopulate France after WWI : 1.5 millions KIA, some millions of wounded and disabled persons.
In fact, about 15.000 Jewish citizens lost their French nationality, from ca 100.000 new Jewish citizens from 1919 to 1939.
Of course, no new naturalizations were given to Jews during this period.
Last but not the least : this de-naturalization applied also to children born in France from these foreign parents.
But in our nation, from French Revolution, we benefit of "jus solis", you are automatically French when you are born on French soil.
These children had no other nationality than being French : by this de-naturalization, they became stateless !
Paris had been liberated on 1944, ca August 25th.
A law passed on October (France had been fully liberated only during 1945 spring) automatically reestablished French citizenship to de-naturalized Jews.
For person who had filled a naturalization file before WWII without being accepted, this file is the "basis" of their inquiry after WWII : this is a proof that these files had been kept for some years (I am sure of that, it had been my father's case and I could copy his documents given in 1939 in his 1948' final file).
I guess that files which hadn't been claimed for a new inquiry after some years, had been destroyed.
In their Finding Aids, National Archives explain there is no list, no index.
You surely know this : in genealogy, there no answer to question you don't ask !
If you give me, by private reply, your father-in-law identity, I could do some searches, I am a full volunteer and I manage the Jewish genealogy workshop of Medem Center - Arbeter Ring of France.