The Dallas Police Department vehicle which pulls over Cliff Barnes' limousine is a final generation (1998-2011) Ford Crown Victoria. Dallas Police Department phased out the Crown Vic prior to 2003 in the wake of vehicle fires when rear-ended (Ford Motor Company installed trunk packs along with an optional fire suppression system since the 2005 model year) where the Dallas Police squads were either a 2003-09 Chevrolet Impala 9C1 or 2006-present Dodge Charger. As of 2013, no Crown Vics are used by the Dallas Police Department (the Dallas County Sheriff squads (white with black hood panels) Crown Vics are still in service until its total phaseout in 2016 or when the squads reach 160,000 miles - law enforcement agencies in the State of Texas usually retire police vehicles when they reach their end of its service life). Also, the white livery with a blue stripe (with the 'Dallas Police' seen in white letters) is no longer used after 2009.
Texas doesn't mandate Gun registration.