Chavan had a licence to carry a revolver, but it had expired on December 31, 2010.
The MLA had, on May 9, 2011, filed an application for the renewal of his firearm licence.
But the application is pending before Deputy Commissioner Sameer Shukla, who is said to be on a long leave. When the MLA left for New Delhi, his wife had mistakenly kept the revolver in his suitcase, sources close to the MLA said.
At the airport the revolver was found during security check of the luggage and the MLA was detained by the police.
The MLA then showed the expired licence and revealed his identity to the airport security personnel.
The police, who were not satisfied with the MLA's explanation, detained him for the night.
The MLA made frantic calls to his colleagues in Karnataka and some officers in Bidar. They later spoke to the airport police and appealed to them to let the MLA continue his journey.
Chavan was let off after the weapon was seized by the airport police. He left for New Delhi by the 6 am flight on Tuesday, to join Chief Minister B S Yeddyurappa and his colleagues, sources said.
