Whether a plaintiff suing a foreign state bears the burden of proving an exception to sovereign immunity or if the foreign-state defendant must disprove the exception, and whether filing a responsive pleading without asserting sovereign immunity as an affirmative defense constitutes a categorical waiver of immunity

Under the Foreign Sovereign Immunities Act of 1976, as amended , 28 U.S.C. 1330, 1441(d), 1602 et seq., a foreign state, including its agencies and instrumentalities, is immune from the jurisdiction of a federal or state court in a civil action unless a claim against it comes within one of the specified exceptions to immunity provided in 28 U.S.C. 1605–1607. The questions presented are: 1. Whether a plaintiff who is suing a foreign state, and thus bearing the burden of establishing that the court has subject-matter jurisdiction, bears the burden of proving that an exception to sovereign immunity applies; or whether instead the foreignstate defendant has the burden to prove that the claimed exception does not apply. 2. Whether a foreign-state defendant categorically waives immunity in an action if it files a responsive pleading without including sovereign immunity as an affirmative defense, irrespective of any other efforts to preserve its immunity in that or in other filings. (ii)