e law, even when the United States is a party." United States 1 O'Block, 788 F.2d 1423, 1435 (10th Cir.198M (citing Oregon ex rel. State Land lid Corvallis Sand & Gravel Co., 429 U.S. 363, 378-81, 97 S.Ct. 582, 60 L.Ed.2d 650 (1977)).7 Second, application of state substantive law directly on point is eminently more logi