What is the principle of absolute and untrammelled "discretion" in public regulation?

The above principle was reiterated by Rand J. in Roncarelli v. Duplessis 1959 CanLII 50 (SCC), [1959] S.C.R. 121. At page 140, Rand J. stated: "In public regulation of this sort there is no such thing as absolute and untrammelled "discretion," that is that action can be taken on any ground or for any reason that can be suggested to the mind of the administrator; no legislative Act can, without express language, be taken to contemplate an unlimited arbitrary power exercisable for any purpose, however capricious or irrelevant, regardless of the nature or purpose of the statute. Fraud and corruption in the Commission may not be mentioned in such statutes but they are always implied as exceptions. "Discretion" necessarily implies good faith in discharging public duty; there is always a perspective within which a statute is intended to operate; and any clear departure from its lines or objects is just as objectionable as fraud or corruption."