Happened to a friend couple of days ago when he was with family passing through cantt checkpost. His car had original rare windows and windscreen tinted (jdm) so the guy at checkpost said in that case you have to get a permit from some army office near. If its not genuine then they have to take it off. The mistake he made was he had front shades and as he was with family he didnt bother to take off shades before crossing checkpost.
A few days later I had to attend a wedding in cantt area and I was confused if they will allow me or not. So I crossed two different checkposts in day time to see their reaction and no one stopped me. My car (jdm) has original tints also. I do have front shades but whenever i cross checkposts I always take front ones off.
