A token that is set to unmodifiable can't be interecated with using the left mouse or mousewheel. However, a user is still able to right click on the token and rotate the token or even delete it! If I manually lock the tockens as the DM client it will prevent the deletion but still not the right click rotation.

function setModifiable( state )

Flags the token modifiability status. Non-modifiable tokens can't be interacted with by the clients.