Actually you can still lock your suitcases. It's not illegal. However, TSA does have the right to cut the locks at any time to gain access to the bag for security checks. In order to avoid having your locks destroyed, you can purchase special TSA approved locks that are able to be opened by TSA agents without being broken. You can find info about this on the TSA website and other places. I had them on my bag for a trip to Chicago from Los Angeles and agents at multiple airports commented positively about them. It seems many people dont even know they're available.