Ever since the news that Disney was in talks to buy Fox, fans have been thrilled with the idea of the X-Men and Fantastic Four joining the MCU. However, upon further review the Fantastic Four’s return to the Marvel universe may not be as simple as it seems.
While Fox does fully own the rights to the X-Men, this is not the case for Marvel’s first family. In 1986 Constantin Films purchased the film rights to the Fantastic Four from Marvel Entertainment and struck a deal with 20th Century Fox in 2004 to distribute any films regarding the Fantastic Four, which included 2005’s Fantastic Four, 2007’s Fantastic Four: Rise of the Silver Surfer and 2015’s The Fantastic Four. So what this all means is that Fox only owns the distribution rights to the Fantastic Four, not the film rights.
This being said, if Constantin Films is unwilling to give the production rights to Marvel, Fox may be able to force their hand since they hold the distribution rights to the property. So while Constantin Films can produce their own Fantastic Four movie, they would have no legal right to distribute it. Meaning it would be in their best interest to give the rights back to Marvel.
But the specifics of the Disney/Fox deal are extremely complicated, so until the announcement of the merger is official it is too early to tell how this will affect Marvel Studios. – Jacob Campbell
Source: We Got This Covered