237 F.3d 919 (8th Cir. 2000)
United States of America, ex rel Crow Creek Sioux Tribe, doing business as Crow Creek Farm Enterprises; Dacotah Farms; Crow Creek Farms; William Shields, Jr., a member of the Crow Creek Sioux Tribe, Individually,  Appellees,v.Hattum Family Farms; Hattum Custom Farms; Robert Hattum, Appellants.
No. 00-1691
United States Court of Appeals FOR THE EIGHTH CIRCUIT
Submitted: December 11, 2000Filed: December 19, 2000

Appeal from the United States District Court for the District of South Dakota.
Before LOKEN, HEANEY, and FAGG, Circuit Judges.
PER CURIAM.


1
Robert Hattum and Hattum Family Farms performed custom farmwork for the Crow Creek Sioux Tribe on tribal land. The Tribe brought a qui tam action against Hattum, seeking to set aside certain crop liens, to require an accounting of payments. Hattum received from the Tribe, and to recover for damages to tribal land. In a counterclaim, Hattum sought damages for unpaid salaries, amounts due under the farming agreements, unjust enrichment, and breach of contract. The district court partially granted the Tribe's motion for summary judgment, concluding the contracts were void under 25 U.S.C.  81 because the Secretary of the Interior had not approved them. See United States ex rel. Crow Creek Sioux Tribe v. Hattum Family Farms, 102 F. Supp. 2d 1154, 1163-64 (S.D. 2000). The district court also concluded the crop lien was void, and found Hattum's affirmative defenses of estoppel, waiver, unjust enrichment, and breach of contract without merit. See id. at 1166. On appeal, Hattum challenges the district court's application of 25 U.S.C.  81 to the contracts and the court's finding that Hattum's affirmative defenses are meritless. Having carefully reviewed the case, we conclude the district court properly granted summary judgment and affirm on the basis of the district court's thorough opinion. See 8th Cir. R. 47B.

