XACE is basically an extension of SELinux into userspace for X11. Given that today Fedora/RHEL are the only distros that enable SELinux out of the box, such an approach would have been doomed to failure (or doomed to provide a product differentiator for RHEL in the best case) - not to mention the sheer joy and excitement that debugging SELinux AVC denials would produce for end users and desktop application developers.

https://www.freedesktop.org/software/XDevConf/x-security-wal...