Dave brings up a good point. The operators are under a contract with the cruise line. That is, the tour is not operated by the cruise line itself. That being said, it is up to the tour operator, not the cruise line, to cancel a tour, as there are other people on the tour not with the cruise line.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)