Thoughts on affirmative defenses

If a tribe operated a parallel organ-matching service, it is unlikely to be a violation of either a federal or state statute relating to organ donation or transplantation. But even if it were a violation of some kind of statute, the tribe would likely enjoy immunity. The actors involved, such as the physicians and nurses performing the operation, may not enjoy such immunity, although one wonders what, if any, statute they would risk violating. At any rate, that's a real concern that is outside the scope of my inquiry.

Focusing on the tribal network itself: if the network is operated by tribes, then the tribes should enjoy immunity from state action. There is authority about tribal businesses not enjoying that immunity, however.  Thus, tribes would need to structure the network within the prevailing legal environment to provide the best possible protection.

I got the following from William C. Canby, Jr., American Indian Law (4th. ed. 2004), 95-102.

If the tribes are immune, they would be immune from states, Kiowa Tribe of Okla. v. Mfg. Techs., Inc., 523 U.S. 751 (1998), but not the federal government, EEOC v. Karuk Tribe Housing Auth., 260 F.3d 1071, 1075 (9th Cir. 2001). Suits might be brought by individuals in federal court, at least in the 10th Circuit, if the claimant is non-Indian and no remedy is available in tribal court, see Ute Distribution Corp. v. Ute Indian Tribe, 149 F.3d 1260, 1266 n.8 (10th Cir. 1998).

Tribal officers can be enjoined, Santa Clara Pueblo v. Martinez, 436 U.S. 49 (1978). Citizens have standing under a federal statute, and tribal immunity is waived, only if expressly authorized in the statute, see Northern States Power Co. v. Prairie Island Mdewakanton Sioux Indian Cmty., 991 F.2d 458 (8th Cir. 1993).

"If a tribally-chartered corporation operates independently of the tribal government and does not engage in governmental functions, however, it may no qualify for immunity in the first place because it is not an arm of the tribe. See Dixon v. Picopa Constr. Co., 72 P.2d 1104 (Ariz. 1989)." Canby, at 102.