Taken from NCL website Guest Conduct Policy

DISCOURTEOUS OR DISRUPTIVE BEHAVIOR
Pool, deck and theater chairs may not be reserved. Topless sunbathing is not permitted except in the designated areas. (Contact Guest Services for more information.)

So there may be some wiggle room no pun intended. <img src="http://www.traveltalkonline.com/forums/images/graemlins/Joy.gif" alt="" />