The rule as I understand it is; If your ship starts the cruise in Hawaii and finishes in another country ie: Mexico, the casino can be open whenever the ship is cruising the islands and is more than three miles from shore. If your cruise starts and finishes in Hawaii you will not see any casino open at any time. This ruling has caused problems for NCL's Hawaiian cruises particularly.
Just came off an 11 night cruise on 'Infinity' departing from Honolulu going to Mexico. Casino open every evening while in Hawaiian territory except the first night when we were docked in Honolulu. After cruising the islands, we cruised for four days on our way to Ensenada. During that time, I do not think the casino ever closed except for early morning hours cleaning.