Comment 2 for bug 778760

I agree with Christophe, though the point stands that if you use a library that doesn't lock its packages ... things are currently harder than necessary to protect against.

Might be we could extend package locking in the inverse direction:

(defpackage :foo
   (:use :cl :some-big-unlocked-package)
   (:restrict t))

(in-package :foo)

(defun from-big-unlocked-package ...)

=> error "Restriction on package :FOO violated while redefining BIG:FROM-BIG..."

Ie. a "restricted package" works as if all other packages were locked, while in it.