  We prove that the singular support of an element in the derived category of
sheaves is $\gamma$-coisotropic, a notion defined in [Vit22]. We prove that
this implies that it is involutive in the sense of Kashiwara-Schapira, but
being $\gamma$-coisotropic has the advantage to be invariant by symplectic
homeomorphisms (while involutivity is only invariant by $C^1$ diffeomorphisms)
and we give an example of an involutive set that is not $\gamma$-coisotropic.
Along the way we prove a number of results relating the singular support and
the spectral norm $\gamma$ and raise a number of new questions.
