SEC v. Texas Gulf Sulphur Co., 401 F.2d 833 (2d Cir. 1968) (en banc), cert. denied, 394 U.S. 976 (1969)
SEC v. Texas Gulf Sulphur is a cornerstone of federal securities law and the modern law of insider trading.
Whether corporate insiders and tippees who possess material, nonpublic information must disclose that information or abstain from trading under Rule 10b-5, and whether TGS's press release, which downplayed known positive exploration results amid market rumors, was materially misleading in violation of Rule 10b-5.
Under Section 10(b) and Rule 10b-5: (1) Any person who possesses material, nonpublic information obtained by virtue of a relationship of trust and confidence with the issuer must either disclose that information prior to trading or abstain from trading until the information is effectively disseminated and the market has had a reasonable time to absorb it (the disclose-or-abstain rule). (2) Information is material if there is a substantial likelihood that a reasonable investor would consider it important in making an investment decision or if it would be expected to significantly alter the "total mix" of information available; for contingent or speculative events, materiality turns on a practical assessment of both the probability the event will occur and the magnitude of its anticipated impact. (3) When an issuer chooses to speak, it must do so truthfully and with a reasonable basis; half-truths and misleading omissions in press releases violate Rule 10b-5. (4) Tippees who trade on material, nonpublic information with knowledge (or reason to know) that it was disclosed in breach of a duty are subject to the same disclose-or-abstain obligation. (5) The SEC may seek equitable relief, including injunctions and orders requiring wrongdoers to relinquish illicit trading profits.
The Second Circuit held that several TGS insiders and certain tippees violated Rule 10b-5 by purchasing TGS securities while in possession of material, nonpublic information about the ore discovery; they were required to disclose or abstain from trading until the information became public and the market had time to assimilate it. The court also held that TGS's contemporaneous press release was materially misleading because it mischaracterized and omitted known positive drilling results, thereby violating Rule 10b-5. The court affirmed the SEC's entitlement to injunctive and equitable relief, including the recovery of illicit trading profits.
Texas Gulf Sulphur is the foundational modern insider trading case. It established the disclose-or-abstain rule, articulated a flexible, investor-centered materiality standard (including for contingent or preliminary information), and underscored that issuers must speak truthfully when addressing the market. The decision also provided practical guidance on when information becomes "public" and extended liability to tippees trading on information they know derives from a breach. The case remains central in law school because it framed core debates that later Supreme Court cases refined: Chiarella and Dirks narrowed the duty analysis to relationships of trust and confidence and clarified tippee liability; Basic endorsed the probability–magnitude approach to materiality in merger contexts; and O'Hagan recognized misappropriation theory. Even with those refinements, Texas Gulf Sulphur's commitments to market integrity, fair disclosure, and the importance of truthful corporate communications continue to guide Rule 10b-5 doctrine and compliance practice.