One or the Other

From a Baltimore Sun article detailing how "red light cameras" are pissing off cops, who no longer can escape speeding tickets through "professional courtesy" (they also argue that the cameras sometimes catch on-duty cops who have a reason to speed but also a reason not to turn on their siren -- for example, arriving at a burglary where they don't want to alert the criminal to their imminent arrival):

Some officers appear to have come up with creative ways to stay red-light-camera-shy. Last year, city police accused two officers of putting stolen license plates on their unmarked cars. The investigation continues, but police sources said at the time that the officers either wanted to prevent drug dealers from recognizing their cars or wanted to avoid getting tickets from the cameras.

Those two possibilities do seem to capture the poles of potential justifiability, don't they?