You don't need permission to fire an employee. You need permission, however, to fire a significant part of your workforce at the same time. Typically you must justify it (for instance because your revenues dropped), and you can't fire in group again until after 18 months have passed.
These rules made much more sense when they came into application mostly during the forties. Back then, just after the war, there were good reasons to be wary of the industry owners, who massively "collaborated" with the Germans (because you know, business is business), and deem them guilty until proven innocent.