Here's my thoughts on this...Is this a public venue or private? Either way it's up to the establishment for policing there policy's and enforcing rules. I do however dislike when they state formal attire and people show up in t-shirt and shorts, but its not up to me to enforce there rules...I say don't let them in or change the attire guidelines. It is considered rude to show up in inappropriate attire knowing what the dress code is. That to me shows disrespect to the establishment and those around that your clearly a "it's all about me" entitled individual and no respect to others.
Last night was our second formal night and i did see people in t-shirts and jeans, t-shirts and shorts (not dressy) with the majority in appropriate attire.
Maybe Royal Caribbean should have those not in designated attire in one dining room and the rest in main dining. Just a thought.