"Page not found" error when I create an alias "legal"

I am using the Path module to create aliases. All of my aliases work fine except for "legal", which gives me a "page not found" error when I try to go to the new alias address.

I've tried variations on legal eg "lega", "egal", even "Legal" with a capital L, all of which work fine! The problem is also specific to this particular site. The "legal" alias works on all our other sites, though none of these are using the same theme.

Any ideas?