Age Thomson
From my memory of a typical gas meter shutoff setup, there is typically a ball valve just before the meter which is designed to accept some sort of padlock. If someone was to have their gas shut off by the utility company, that valve would be closed and a tamperproof lock would be put through the holes of the 2 pieces of that valve. Now, if someone was expecting that this might happen, and they placed some sort of tamperproof device (example a padlock) through only one of those two holes, then the ball valve would not be able to be fully closed without removing that device first. Those gas guys have trucks full of tools though so I doubt it would do much for long...