Summary

Portrait of Morrison Waite Morrison Waite Munn v. Illinois — Opinion of the Court

The controlling fact is the power to regulate at all. If that exists, the right to establish the maximum of charge, as one of the means of regulation, is implied. In fact, the common-law rule, which requires the charge to be reasonable, is itself a regulation as to price. Without it the owner could make his rates at will, and compel the public to yield to his terms, or forego the use.
But a mere common-law regulation of trade or business may be changed by statute. A person has no property, no vested interest, in any rule of the common law.
Source: Wikisource

Portrait of Morrison Waite Morrison Waite Munn v. Illinois — Opinion of the Court

In countries where the common law prevails, it has been customary from time immemorial for the legislature to declare what shall be a reasonable compensation under such circumstances, or, perhaps more properly speaking, to fix a maximum beyond which any charge made would be unreasonable. Undoubtedly, in mere private contracts, relating to matters in which the public has no interest, what is reasonable must be ascertained judicially.
Source: Wikisource

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