We use those zip ties. It keeps the luggage from coming open, and if they need to be searched, then all they have to do is cut them. If you do use zip ties, and you forget to take something to cut them with once on board, the ice tongs work get for this.
I use ty raps and carry extras in the luggage for the return trip home. Seems to work really well. But make sure you bring some kind of scissors or clippers to remove from the luggage when your luggage arrives in your cabin.
We too use colored tye wraps, and that way the luggage is secured from "popping open", and you can tell if security, or anyone else opened your luggage. Works really well, and in fact, I don't think we've ever had any of our bags opened.
Since we have to fly to any port, I use TSA approved locks on the suitcases. Just leave them on for the ship also.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08
Like Irish, I use the TSA locks. They have an indicator to let you know if your luggage was opened. When we went to Vancouver, my mother's lugggage was searched and lock put back on. No problems at all.