Cyril E. King airport is federal, not territorial. TSA is there, federal sniffer dogs are there, and federal drug law says cannabis is illegal. Whatever you bought in Charlotte Amalie or Red Hook stays on St. Thomas when you fly out.
Same story for the ferry to St. John, the seaplane to St. Croix, and every charter route between the islands. Each of the three U.S. Virgin Islands is its own regulated cannabis market, and inter-island transport isn't authorized. The ferry from Red Hook to Cruz Bay is a twenty-minute crossing inside U.S. waters, but the cannabis rule treats each island as its own market. Buy on the island where you plan to consume.
Cruise ships are federal jurisdiction too. Every major cruise line bans cannabis in its guest terms, and getting caught at the gangway can mean confiscation, being left behind in port, or worse. The traveler forums are full of these stories; don't add to them.