Long story short: The Oceania letter says that "we have just been informed by our port agent in Libya that in recent weeks the governments of the United States and Libya have been feuding because, apparently, the U.S. denied entry into the United States to a Libyan diplomat." In a purely retaliatory move, reports Oceania's Tim Rubacky, ships calling at either Benghazi or Tripoli -- the key Libyan ports -- can disembark non-American passengers; U.S. travelers must stay onboard.
On its part, Oceania plans to replace the calls if the embargo against U.S. tourists is still underway. Other cruise lines, such as Silversea and Orient Lines, reportedly did make scheduled stops there -- and Americans were kept onboard though calls to spokespeople at both lines for confirmation were not returned.
This is the third time a political issue in the Mediterranean that has absolutely nothing to do with travelers, U.S. or otherwise, has impacted cruise passengers. In October, a strike by ferry workers in Marseilles hampered cruise calls there and at Corsica. Just last week, a strike in Spain by fisherman over fuel prices resulted in major disruption of embarkation and disembarkation for ships such as Crystal Serenity and Royal Caribbean's Brilliance of the Seas.