In addition, some columnists and think tank analysts have argued that U.S. accession to the Convention would interfere with the Proliferation Security Initiative (PSI), under which the United States and more than a dozen allies have agreed to interdict some ships that may present a nonproliferation risk. In fact, the Convention expands the list of justifications for ship interdictions set forth in its predecessor, the 1958 Convention on the High Seas, to which the United States has been a party for more than forty years. Among the many legal bases that may be applicable to interdictions under the PSI are the jurisdiction of coastal states in their territorial seas, the right to board stateless vessels, an agreement concerning high-seas boarding with a flag state (the country of origin of an oceangoing vessel) and the inherent right of self-defense. Indeed several allies have recently expressed concern about the U.S. failure to ratify the Convention, asserting that this failure could weaken the PSI.