Tenn. Code Ann. § 55-9-414 (2005)
Blue flashing emergency lights on motor vehicles unlawful -- Exception -- Penalty
(a) (1) It is unlawful for anyone to install, maintain or exhibit blue flashing emergency lights or blue flashing emergency lights in combination with red flashing emergency lights, except full-time, salaried, uniformed law enforcement officers of the state, county, or city and municipal governments of the state, and commissioned members of the Tennessee bureau of investigation when their official duties so require as defined by §§ 38-8-106 and 38-8-107.
(2) A violation of subdivision (a)(1) is a Class C misdemeanor.
(b) (1) The prohibition in subsection (a) does not apply to the motor vehicles of constables who are wearing law enforcement uniforms designated by the governing body of the county in which they serve in those counties in which such constables retain law enforcement powers and duties under the provisions of §§ 8-10-108, 39-17-505, 40-6-210, 55-8-152, 57-5-202 and 57-9-101.
(2) The provisions of this subsection (b) apply only to those counties having a population of:
not less than nor more than
------------ -------------
11,100 11,200
11,500 11,600
13,975 14,500
43,000 44,000
65,750 66,000
70,000 74,000
according to the 1970 federal census or any subsequent federal census.
(c) The prohibition of subsection (a) does not apply to official motor vehicles of the sheriff's department being operated by reserve or auxiliary deputy sheriffs duly authorized by the sheriff and appointed pursuant to title 8, chapter 20. Such reserve or auxiliary officers operating departmental vehicles shall be in uniform and carry appropriate identification issued by the sheriff. The provisions of this subsection (c) apply only in counties having a population of not less than forty-three thousand seven hundred (43,700) nor more than forty-three thousand eight hundred (43,800) according to the 1980 federal census or any subsequent federal census.
(d) The prohibition of subsection (a) does not apply to motor vehicles of specially commissioned police officers employed pursuant to § 49-7-118(f) when operating either within five (5) miles of any property owned or operated by the colleges or universities referenced therein, or as may be directed by the chief law enforcement officer of the applicable county.