YES If You're a Police Officer. in Los Angeles...lol.
They are not illegal in my state, but you may be charged with carrying a concealed weapon, on posession of a weapon dangerous to the public peace. Don't let anyone tell you they are a prohibited weapon. They are not.
As I said in the other thread on this, spring batons are illegal (prohibited), gavity batons such as ASP are not. You run the same risk with it as you do with anything you might carry of falling under a "weapon" definition. However, as for prohibitions, the ASP is as legal as carrying a pocket knife or walking stick. Any of these items can be defined as a "weapon" dependent upon circumstances, as you are well aware.
An asp can be a tool like any other. It can also be used for defense against animals, or used to extend ones reach. It can simply be classified as an emergency tool, window breaker for escape during a car accident or trapped in a building fire. Also, if you aren't waving it around, you won't draw attention to yourself. As such it is easily enough justified. As a knife is easily justified. A walking stick can be used as a weapon, but can be justified as well. That's really the point I was trying to clarify. The spring batons are, by law, prohibited, the asp style gravity batons are not just like a walking stick is not prohibited by law.