Guards

  Guard settings control access to the transitions, variables or work
  lists. If a user possesses any of the permissions or roles
  specified, or if one of the expressions evaluates as true, then
  whatever is being guarded is accessible. If no permissions, roles
  or expressions are specified, access is automatically granted.
 
  You can supply several options in each field by separating them with
  a semicolon.

  The context in which the guards evaluate permissions and roles is
  obviously important. In the case of transitions and work lists, it 
  depends on the category. If it's 'worklist', then the context is 
  that of the content object, and local roles will behave just as
  you'd expect. If the category is 'global', then the context will be
  the site root, so the local roles between the site root and the
  content won't be considered.

  [**Note:** What about variables?]