Rule of reason

These critics emphasized in particular the Court's decision in United States v. Trans-Missouri Freight Association, 166 U.S. 290 (1897), which contains some language suggesting that a mere restriction on the autonomy of traders would suffice to establish that an agreement restrained trade within the meaning of the Act.

In an opinion written by Justice Louis Brandeis, the Court held that an agreement between rivals limiting rivalry on price after an exchange was closed was reasonable and thus did not violate the Sherman Act.

The rule was narrowed in later cases that held that certain kinds of restraints, such as price fixing agreements, group boycotts, and geographical market divisions, were illegal per se.

More recently, the Supreme Court has removed a number of restraints from the category deemed unlawful per se and instead subjected them to fact-based rule of reason analysis.

Moreover, the Supreme Court has reaffirmed the conclusion in Standard Oil that analysis under the rule of reason should focus on the economic but not the social consequences of a restraint (National Society of Professional Engineers v. United States, 435 U.S. 679 (1978)).