My son is under simple guardianship (curatelle simple) and I am his guardian (curateur). He has found an apartment and is about to sign the lease. I won’t be able to attend the signing. Can he sign it without my involvement?

Yes. Even though your son is under guardianship, he retains the capacity to perform certain legal acts independently. Your intervention is only required for more serious acts, for which a guardian would need judicial authorisation, as specified in Article 467 of the French Civil Code. Signing a residential lease for a term of less than nine years is considered an act of administration, which does not fall into that category. This is confirmed by Decree No. 2008-1484 of 22 December 2008, Annex 1.