What constitutes a baton is not totally clear in the "eyes of the law." The law is ambiguous at best, in respect to so-called Telescopic Batons or Expandable Batons.
The below list of expandable baton laws includes states that have laws restricting the use or possession of expandable batons or other similar weapons. Expandable batons can be called expandable billys, billies, billy clubs, batons, telescopic batons, clubs, bludgeons and several other names. Expandable baton laws can sometimes be tricky, and they can often be grouped with weapons that are similar, such as the blackjack, slungshot, sandclub, sap, or sandbag or billys.
Many places in the United States have prohibited offensive weapons laws which allow you to carry certain weapons such as expandable or telescopic batons. They become illegal though if you use or intend to use the device in an offensive manner. This results in additional charges or stiffer consequences. One would think this type of law would allow you to use and carry the weapon for defensive purposes without question.
Unfortunately, it is difficult to identify telescopic batons as illegal in most states as they do not specifically mention expandable or telescopic batons.
We have not found a state law from any state that mentions expandable baton laws or telescopic baton laws. In some locations, an expandable baton falls under the term "club," "billy" or "bludgeon" and therefore it would be illegal. If you carry an expandable baton in states that mention club, billies or bludgeons as illegal in any way you run the risk of being prosecuted.
State by State
New York State
Washington DC (District of Columbia)