On another cruise line, they do not allow irons in staterooms because of a fire hazard. I don't know about Norwegian. You may want to check their policy on bringing irons on board.
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)