When the inodes are cached by fuse (non-zero attr_timeout), and the standard_permissions are used, the following sequence :

chmod 755 trydir
rm -rf trydir
mkdir trydir
echo file > trydir/file
ls -li trydir/file    
chmod 000 trydir
chmod 444 trydir/file
ls -li trydir/file

outputs :

293 -rw-rw-r-- 1 linux linux 5 2009-08-25 17:50 trydir/file
293 -r--r--r-- 1 linux linux 5 2009-08-25 17:50 trydir/file

The "chmod 000" should have led to an EACCES error for the subsequent commands.

This was reported in 2009 (http://article.gmane.org/gmane.comp.file-systems.fuse.devel/8099), and according to http://article.gmane.org/gmane.comp.file-systems.fuse.devel/15300 some work is still needed on it.

This means that for being Posix compliant, fuse file systems cannot either use the cache or have the permissions checked by the kernel.