Mason v. Pewabic Mining Company was a case heard by the Supreme Court of Michigan in 1891. The case involved a dispute between the Pewabic Mining Company and the Mason family over the ownership of a mining claim. The Mason family had been working the claim since 1876, but the Pewabic Mining Company had recently acquired the rights to the claim. The Masons argued that they had acquired a valid possessory title to the claim, while the Pewabic Mining Company argued that the Masons had not acquired a valid possessory title. The Supreme Court of Michigan held that the Mason family had acquired a valid possessory title to the claim. The court found that the Mason family had been in continuous possession of the claim since 1876, and that they had made improvements to the claim and had paid taxes on it. The court also found that the Pewabic Mining Company had not taken any steps to assert its rights to the claim until after the Mason family had acquired a valid possessory title. The court concluded that the Mason family had acquired a valid possessory title to the claim, and that the Pewabic Mining Company had no right to the claim.

In the case of Mason v. Pewabic Mining Company, Justice Field delivered a dissenting opinion. He argued that the majority’s decision was wrong because it failed to recognize that Congress had already granted exclusive rights to mining companies in certain territories through its legislation and treaties with Native American tribes. Furthermore, he contended that if Congress did not intend for these exclusive rights to be respected by state courts, then they should have been more explicit about this when enacting their laws or entering into treaties with tribal nations. Additionally, he noted that while states may have some authority over public lands within their borders, this does not extend to private property such as mines owned by corporations like Pewabic Mining Company; thus any attempt by Michigan's legislature or court system to interfere with those rights would be unconstitutional under the Supremacy Clause of the U.S Constitution which grants federal law precedence over state law in matters involving interstate commerce and foreign affairs (such as treaty obligations). In conclusion, Justice Field concluded his dissent by asserting that since no clear evidence existed indicating an intent on behalf of Congress for states' courts to disregard existing mining company privileges granted through federal legislation and/or treaty agreements between Native American tribes and the United States government - Michigan's Supreme Court should have ruled in favor of Pewabic Mining Company instead of overturning its lower court ruling granting them exclusive mineral rights on land located within Michigan's boundaries