The cruise lines personell (whom sandman suggests talking to), if they even knew a minutia legal detail like that to begin with, probably would have gotten their answer (like if they'd been asked that question in the past by other guests), by asking powers-that-be in whatever country/state they dock in. Ie.: who better to ask, than a bureaucrat, in whatever locale you're going to, right?

Herein lies the problem: this has been done before (ask a lawyer or consoluate type in the state/country you intend to vacation in) and PRESTO, you get a "no". Why? Because the person being asked is couching their answer in terms of shipwreck salvor laws, raiding the pyramaids, exporting gold bars, or other such things.
As an example, there has been many persons over the years, wondering if they can metal detect on Mexican tourist beaches. They get a "no" by the above means, so they leave the detectors at home. Imagine their surprise when the arrive for their vacation, and see other guys md'ing the tourist beaches, with no problems. In fact, there are even dealers there in the major cities in Mexico, South America, etc.... doh!
So sure, ask an employee of the cruise-ship if you want. But they're going to give you the safe or technical answer (ie.: "don't walk in dark alleys" etc....), and it may not be the in-actual-practice answer. Ie.: no one may really care less. But since you asked.........