Thurgood Marshall delivered the opinion of the court. Marshall noted that the tribe had a properly formed constitution, approved by the Secretary of the Interior, and that it included that the tribal council may impose taxes on non-members doing business on the reservation. He noted that the tribe had executed oil and gas leases for about 69% of the reservation and that the leases provided for royalties to be paid to the tribe. Marshall further noted that the tribe followed the proper process to enact a severance tax, obtaining the approval of the BIA as part of the process. The first argument of the oil companies that the power to tax only arose from the power of the tribe to exclude persons from the reservation. Marshall disagreed, stating that the power to tax is an inherent attribute of a tribe's sovereignty. Tribal government includes the need to provide for services, not only to the tribe, but to anyone doing business on the reservation. He noted that the oil companies benefited from police protection and other governmental services. Citing Colville, he stated that the tribe's interest in raising "revenues for essential governmental programs . . . is strongest when the revenues are derived from value generated on the reservation by activities involving the Tribes and when the taxpayer is the recipient of tribal services." Marshall noted that Congress was able to remove this power, but had not done so, and had acknowledged in 1879 the power of the Cherokee Nation to tax non-Indians. Marshall further noted the oil companies' arguments that a lease would prevent a governmental body from later imposing a tax would denigrate tribal sovereignty, and that tribal sovereignty was not limited by contractual arrangements. Only the Federal government has the authority to limit the powers of a tribal government, and a non-Indian's consent is not needed (by contract or otherwise) to exercise its sovereignty, to the contrary, the tribe may set conditions and limits on the non-Indian as a matter of right. "To presume that a sovereign forever waives the right to exercise one of its sovereign powers unless it expressly reserves the right to exercise that power in a commercial agreement turns the concept of sovereignty on its head." Marshall then addressed the Commerce Clause issues, and the argument of the Solicitor General that the section of the Commerce Clause that dealt directly with Indians applied rather