[development] Filter taxonomy

Hi, In my configuration, I have users who belong to organic groups who can create "projects" nodes. Upon creation, these "projects" node automatically create taxonomy terms using the NAT module. Now, I would like to propose to the user only the "projects" terms he created (acctually, the ones created by people of his group as well, but if I can do one, I can do the other). Is there a module, a hook or a way to filter out some terms when a node is edited/added by a user that is not allowed to use these terms? At the moment, I have patched taxonomy.module but it would be nice to have something maybe like hook_taxonomy() with a "load" operation? -- Golgote Blog : http://golgote.freeflux.net