In the case of Monamotor Oil Co. v. Johnson, Treasurer of Iowa et al., 1933, the U.S Supreme Court dealt with a dispute over an Iowa state tax law that imposed a levy on oil companies operating outside the state but selling within it. The plaintiff, Monamotor Oil Company argued that this was unconstitutional as it violated both due process and equal protection clauses under the Fourteenth Amendment since they were being taxed differently than in-state businesses conducting similar operations. However, after examining all aspects of the case including previous rulings and interpretations related to interstate commerce and taxation laws, the court upheld Iowa's right to impose such taxes. It ruled that there was no violation of either clause because out-of-state corporations like Monamotor could be treated differently if their business model differed from those operating solely within state boundaries. The court also noted that while states cannot impede interstate commerce through discriminatory or excessive taxation - which would violate constitutional principles - they do have broad powers to regulate local activities affecting public interest even if these involve interstate transactions.

In the dissenting opinion for Monamotor Oil Co. v. Johnson, it was argued that the Iowa statute in question did not violate the Commerce Clause of the U.S. Constitution as majority opined. The dissenting justices believed that this law merely regulated business within its borders and did not impose a direct burden on interstate commerce, thus falling within state's police power to protect public welfare and safety by ensuring quality control over petroleum products sold in Iowa. They contended that any incidental effect on interstate commerce was permissible under existing precedents which allowed states to regulate local aspects of commerce even if they indirectly affected out-of-state businesses or transactions crossing state lines.