The Socony-Vacuum Oil Co. v. Smith case in 1938 involved the United States Supreme Court ruling on a violation of antitrust laws by major oil companies, including Standard Oil and Vacuum Oil Company (now part of ExxonMobil). The companies were accused of price-fixing through an illegal buying program that aimed to control surplus gasoline on the spot market to stabilize prices during the Great Depression. The court ruled unanimously against these corporations, stating that any form of price manipulation or fixing constitutes a per se violation under Section 1 of the Sherman Antitrust Act - meaning it is inherently illegal regardless of its effect on competition or justification behind it. This landmark decision reinforced federal commitment to free-market principles and set precedent for future cases involving anti-competitive practices.

In the dissenting opinion for the Socony-Vacuum Oil Co. v. Smith case, it was argued that there was no evidence of a conspiracy to raise prices or create a monopoly, which are key elements in proving violation of the Sherman Act. The dissenting justices believed that buying surplus oil to prevent price collapse during times of oversupply should not be considered illegal per se under antitrust laws as it could also be seen as an effort to stabilize market conditions and protect business interests. They contended that such actions did not necessarily equate to manipulation or control over prices but were rather measures taken in response to existing market situations. Furthermore, they expressed concern about how this ruling might impact other businesses who engage in similar practices out of necessity due to fluctuating supply and demand dynamics.