I don't know if I'd necessarily get pulled over for it, but it won't pass annual state inspection in VA for sure:
"D. Inspect for and reject if...
... Every passenger car manufactured for the 1986 or subsequent model year and multipurpose passenger vehicle, truck, or bus whose overall width is less than 80 inches, manufactured September 1, 1993, and subsequent model year is not equipped with a supplemental center high mount stop lamp of an approved type (DOT or SAE-U, U1 or U2) mounted at the vertical centerline of the vehicle that functions only in cooperation with the vehicle's brake lights and hazard lights. Any other vehicle on which a supplemental center high mount stop lamp is mounted shall have the lamp mounted at the vertical center line of the vehicle. The lamps shall be of an approved type and shall function only in conjunction with the stop lamps. The high mount stop lamp must be steady burning and not wired to flash with turn signals or other wig-wag device"...
(19VAC30-70-560)