John L. McMahon, Junior v. John J. Christmann

Summary

The Texas Supreme Court reversed the Court of Civil Appeals and remanded for trial on the respondents' cross‑action for reformation, holding that the oil, gas and mineral lease reserves a total royalty of 5/96 of production and that the proportionate reduction clause does not apply to the overriding royalty because the clause expressly states "without reduction." The Court also declined to apply the Duhig estoppel rule to mineral leases. Justice Smith concurred and Justice Garwood dissented, each contesting the majority's approach to the Duhig rule.