Can a Commissioner's Directive that imposes monitoring of inmates' phone calls be prescribed by law?

In Hunter v. Canada (Commissioner of Corrections), 1997 CanLII 6355 (FC), [1997] 3 F.C. 936 (F.C.T.D.), a commissioner’s directive that among other things, imposed monitoring of inmates’ phone calls, was found to be “prescribed by law” because the authority to create the directive flowed from particular statutory provisions and there was “no disruption in the chain of statutory authority flowing from the Act and the Regulations to the limits in Commissioner's Directive 085" (para. 70).