“The courts are not bound by mere forms, nor are they to be misled by mere pretences. They are at liberty — indeed, are under a solemn duty — to look at the substance of things, whenever they enter upon the inquiry whether the legislature has transcended the limits of its authority. If therefore, a statute purporting to have been enacted to protect the public health, the public morals, or the public safety, has no real or substantial relation to those objects, or is a palpable invasion of rights secured by the fundamental law, it is the duty of the courts to so adjudge, and thereby give effect to the Constitution.” Mugler v. Kansas, Source: Mugler v. Kansas, 123 U.S. 623, 661.
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