## Facts

- The Coal Lands Acts of 1909 and 1910 authorized land patents conveying the surface and other interests while reserving “coal” to the United States.
- Certain patented lands were within areas previously ceded by the Southern Ute Indian Tribe; in 1938 the United States restored to the Tribe, in trust, federal title to remaining ceded lands, including the reserved coal in these patented tracts.
- The coal seams under the patented lands contain coalbed methane (CBM), which was historically treated as a dangerous by-product of coal mining but later became a commercially valuable energy resource.
- A 1981 Department of the Interior Solicitor opinion concluded that the Acts’ reservation of “coal” did not include CBM; producers and royalty owners developed CBM under leases from private owners rather than from the coal owner.
- The Tribe sued, seeking a declaration that CBM is part of the “coal” reserved by the Acts and therefore part of the Tribe’s restored coal estate; during litigation, Interior withdrew the 1981 opinion and supported the Tribe’s position.
- The district court granted summary judgment for the producers, concluding “coal” referred to a solid substance and excluded gas; the Tenth Circuit (en banc) reversed, finding ambiguity and applying the rule that ambiguities in public land grants are resolved in favor of the sovereign.

## Issues

1. Whether “coal” reserved to the United States under the Coal Lands Acts of 1909 and 1910 includes coalbed methane gas located within coal formations.
2. Whether a court may treat “coal” as ambiguous and apply a sovereign-favoring canon to place CBM within the reserved coal estate.

## Decision

- The Supreme Court reversed the Tenth Circuit (7–1).
- The Court held that, as used in the 1909 and 1910 Acts, “coal” does not include CBM gas.
- The Court reasoned that the controlling meaning is the ordinary understanding at the time of enactment, when coal was understood as a solid fuel and CBM was viewed as a distinct, hazardous gas released during mining.
- Because the term was not ambiguous in its historical context, the Court declined to apply the sovereign-favoring canon relied on by the Tenth Circuit.
- As a result, CBM is not part of the reserved coal estate and does not pass to the Tribe solely by virtue of its coal ownership.

## Legal Principles

- Mineral reservations in federal land patents are construed according to the ordinary meaning of the reserved term at the time Congress enacted the reservation.
- Under the Coal Lands Acts of 1909 and 1910, “coal” denotes the solid mineral fuel historically mined and marketed, not gases associated with coal seams.
- Technological and economic developments that later make a resource valuable do not expand a statutory mineral reservation beyond its historically fixed meaning.
- Interpretive canons favoring the sovereign in public land grants do not apply where the statutory term, read in historical context, is not ambiguous.

## Conclusion

The Court held that the Coal Lands Acts’ reservation of “coal” excludes coalbed methane, allocating CBM to the non-coal estate and limiting the use of sovereign-favoring canons when the reserved mineral term has a settled historical meaning.


Amoco Prod. Co. v. S. Ute Indian Tribe, 526 U.S. 865 (1999)