No, `can` / `require` / `check` / `guard` usually (apart from `check.perm` etc.) perform authorization checks within the `adhocracy.lib.auth.xxx` namespaces. We could add a `freeze` method to `...lib/auth/proposal.py`, which just does `check.perm('proposal.freeze')`, but this isn't needed here, as we can check the permission directly. Instead of the above, we could do `has('proposal.freeze')`, which might be a bit cleaner, but it's the same anyway.