There's probably a law that nobody would ever enforce. The uproar would sink
some minor functionary's entire career in public employment.

A few ashes tossed overboard as a memorial don't present a serious pollution
hazard. If you were a chimney cleaning company hoping to shovel a pickp load
into the local harbor every afternoon at quitting time.....that would be
another matter entirely.

Sorry about your loss. Your departed friend
was lucky to have people willing to treasure his memory and honor his passage
with a sincere ceremony.