10 U.S.C. § 434
Reservation of defenses and immunities
The submission to judicial proceedings in a State or other legal jurisdiction, in connection with a commercial activity undertaken pursuant to this subchapter, shall not constitute a waiver of the defenses and immunities of the United States.
(Added Pub. L. 102–88, title V, § 504(a)(2) , Aug. 14, 1991 , 105 Stat. 439 .)