You could put a lock on the zippers but it really wouldn't lock the main compartment. From the top it uses a draw string like many other bags. From the side access to the main compartment and other pockets there are zippers and a lock could be put on these. However, the pull tabs are strings and could easily be cut.

Technically, you can but if the robber was determined, he can just cut the straps that you put the lock onto. There are no metal pull tabs to put a lock on.