Might be better off just instituting pollution taxes and not letting ships fly whatever flags they want or burn whatever oil they want. Then if cruises can clean up, good for them.
There are some things that are just plain Bad and should be illegal, like theft.
There are other things that aren't really great for us, but we (well, some of us) derive pleasure from them, or some of us do. Like alcohol, tobacco, cannabis, eating beef, and so on.
The best thing to do with those is not outlaw them, but tax them.
This is harder than it seems, there are international treaties that "regulate" (read: de-regulate) what companies can do regardless of the country.
Also in many cases a particular city, say Barcelona or Venice, may want to regulate, but pollution laws are typically at the regional or national level.
I can't read the article btw