Amends the Foreign Sovereign Immunities Act to restrict damages in admiralty cases for improper arrests to the damages incurred during the detention. Authorizes suits to enforce a maritime lien in rem. Provides that a decree against a foreign state may not be an amount greater than the value of the vessel or cargo upon which the lien arose. Grants to U.S. courts jurisdiction over a foreign state in a case brought to foreclose a preferred mortgage as defined by the Ship Mortgage Act.