O'Hagan Law refers to a legal principle established in the case of O'Hagan v. United States, which addresses insider trading. The ruling clarified that individuals can be held liable for trading securities based on nonpublic information obtained from a fiduciary relationship, even if they did not directly misappropriate the information. This principle emphasizes the importance of trust and confidentiality in financial transactions. It aims to maintain fair market practices by preventing individuals from exploiting privileged information for personal gain, thereby promoting integrity within the securities market.