Boot guns work on a simple principle.  Normally, a person can only exit or enter The City from a house that they have access to.  Some allowances are made for access interruptions such as computer failure and power outages, but improper logouts are considered criminal offenses.  This was because beta users developed ‘Dropout Syndrome.’  Midas created user houses and covered up the damage.  But they made Boot Guns to drop problem users.  Which is why Cynthia was surpassed to find her gun had no effect on the man groaning and thrashing in the street.  He lunged at her and howled.