Nobody outside of the Marvel Studios, Fox or Sony offices knows for sure who owns what, but we do know that some characters wind up in a bit of a grey area.
A fan asked Gunn on Twitter “why are the Kree available but the Skrulls are at Fox.
Thanks to a recent Tweet from Guardians of the Galaxy director James Gunn, we now know that the Skrulls fall into that grey area.
Gunn probably has a very extensive, working knowledge of what characters are and are not owned by Marvel Studios at the moment.