A lawful nonconforming structure may be maintained, repaired, remodeled, enlarged or structurally altered so long as the nonconformity is not extended, enlarged or in any way made more nonconforming to the requirements of the ordinances of the village of Arena. Except as expressly authorized by the preceding sentence, a lawful nonconforming structure shall not be extended, enlarged, reconstructed, moved or structurally altered, except when required to do so by law or order.