In the 1902 case of Clarence E. Collins v. State of New Hampshire, the U.S Supreme Court upheld a state law that prohibited door-to-door sales without a license. The plaintiff, Collins, was convicted for selling his goods in this manner without obtaining the necessary permit from local authorities as required by New Hampshire's laws at that time. He challenged his conviction on constitutional grounds arguing it violated his Fourteenth Amendment rights to due process and equal protection under the law because he believed it interfered with interstate commerce and unduly restricted personal liberty and private property rights. The Supreme Court disagreed with Collins' arguments stating that states have inherent police power to regulate certain business practices within their borders for public welfare purposes including preventing fraud or deceit in sales transactions which could occur through such unregulated activities like door-to-door solicitation. Therefore, they found no violation of any constitutional right in requiring licenses for these types of commercial activities.

In the dissenting opinion for Clarence E. Collins v. State of New Hampshire, Justice Harlan argued that the state law requiring a license to sell merchandise on public property was unconstitutional as it violated the Fourteenth Amendment's Equal Protection Clause. He contended that this law unfairly targeted certain individuals and businesses while exempting others without any reasonable basis or justification, thus creating an arbitrary and discriminatory classification system. Furthermore, he believed that such licensing requirements interfered with citizens' fundamental right to earn a livelihood in common occupations and trades by imposing unnecessary restrictions and burdens on their economic activities. Therefore, according to Justice Harlan, this legislation not only contravened principles of equal protection under the law but also infringed upon individual liberties protected by due process rights.