Originally Posted by You
Is there a clause stipulated somewhere which states the fare-paying passenger MUST comply wth a dress code?
On many cruise lines, yes. Many cruise lines now have a "passenger conduct policy" which you are required either to sign or affirm digitally before embarkation, which states explicitly that failure to conform to the published dress code is a violation. In flagrant cases, failure to conform is sufficient grounds for the ship to leave the passenger in the next port of call.