Vermont officials are preparing to seize a Civil War era cannon at the center of a longstanding and pitched battle between the state and a group of historic re-enactors.

The bronze, 12-pound Napoleon cannon paid for by the Proctor family is owned by the state but has been maintained, repaired and used for three decades by re-enactors from the 2nd Battery Vermont Light Artillery — named after the original unit that used the cannon.

That arrangement worked comfortably until the state ordered the re-enactors to stop firing the gun to both preserve it and protect the public from injury....