Yes, There IS a Dress Code in Hawaii.

On my flight back home from Los Angeles last month, there was a nice young couple from Los Angeles sharing the row with me. They were going to be spending a week here on Maui.
After we landed, I saw them again briefly in the Baggage Claim area where they were struggling with four large suitcases. I see that all the time and always wonder at it. People vacationing here will be spending virtually all day every day in shorts and T-shirts and probably every night in shorts and aloha shirts, too. So why all the baggage?
You really don’t need a lot in the way of wardrobe, even if you live here. I have one sport coat which I wear twice a year at two NARP meetings on the mainland. I did have a suit for a while, but I gave it away probably 30 years ago.
There is almost no occasion here in Hawaii for which a nice pair of slacks, dressy shoes, and an aloha shirt is not acceptable attire for a man. Women dress up or down accordingly.
 In fact, the difference between formal and informal wear for men in Hawaii is pretty simple: at the office and for weddings and funerals, your aloha shirt is tucked in. (I should note that aloha shirts worn to work tend to be in darker colors and a little more conservative in design.)
The rest of the time, if it’s an informal gathering—a backyard luau, for instance—your shirt tails are out. In or out. Formal or informal. That’s pretty much it.
There are a couple of exceptions: most legislators wear a coat and tie during official meetings of the House or Senate. And it’s also formal attire—meaning dark suits and ties—for anyone officially involved in court proceedings: meaning the lawyers and prosecutors.
Aloha shirts are fine for witnesses and jurors. But tucked in is preferred.