While this may be a reasonable use case (though personally I might dispute that), what's to stop them from using the same system to fine everybody with expired

While this may be a reasonable use case (though personally I might dispute that), what's to stop them from using the same system to fine everybody with expired registration? One crime is obviously more serious than the other, but how serious must a crime be to warrant the use of mass surveillance as an enforcement tool? Where does one draw the line?