In the case of O'Neill v. Leamer in 1915, the U.S Supreme Court ruled on a dispute involving land ownership and mining rights. The plaintiff, O’Neill, claimed that he had been fraudulently induced into selling his property to Leamer by being misled about its value and potential for mineral extraction. He sought to have the sale set aside so he could reclaim his property. However, the court found no evidence of fraudulent misrepresentation or concealment on part of Leamer during negotiations for purchase; rather it was determined that both parties had equal access to information regarding the land's worth and potential resources at time of transaction. Therefore, it upheld lower courts' decisions denying O’Neill’s claim stating that buyer's remorse does not constitute grounds for reversing a contractually agreed upon sale.

The dissenting opinion in the O'Neill v. Leamer case argued that the majority's decision was an overreach of judicial power and a violation of states' rights. The dissenters believed that the Supreme Court had no authority to interfere with Pennsylvania's tax laws, as they were not violating any federal law or constitutional provision. They contended that it was up to each state to determine its own taxation policies, even if those policies might seem unfair or discriminatory from an outside perspective. Furthermore, they pointed out that there were other legal avenues available for challenging these taxes - such as through state courts - which should have been pursued before bringing the issue before the Supreme Court. In their view, by stepping in and overturning Pennsylvania's tax laws without clear justification under federal law or constitutionality issues, the court was undermining principles of federalism and setting a dangerous precedent for future cases.