In a world where everybody speeds and nobody gets ticketed for minor infractions of the limit, the police have a unique power: they can choose who to pull over by any criteria they want (including biases such as racism) under the guise of enforcing the speed limit. This results in our effective laws (those that are enforced, rather than those on the books) being defined by the police themselves:
As drivers on our highways know well, American law often means something other than what it says. Roadside signs define the speed limit, or appear to do so: 65 or 70 miles per hour on well-built highways, 25 or 30 on local roads in residential areas, something in between for local highways and main roads in business districts. But drivers who take those signs seriously are in for a surprise: drive more slowly than the posted speed limit in light traffic and other drivers will race past, often with a few choice words or an upraised middle finger for a greeting. In the United States, posted limits don’t define the maximum speed of traffic; they define the minimum speed. So who or what determines the real speed limits, the velocity above which drivers risk traffic tickets or worse? The answer is: whatever police force patrols the relevant road. Law enforcers — state troopers and local cops — define the laws they enforce.
The net effect is a drastic increase in the power of each police officer and of enforcement agencies in general:
That power to define the law on the street allows the police to do two things they otherwise couldn’t. First, state troopers can be selectively severe, handing out fines for driving at speeds no higher than most cars on the road. Second, those same state troopers can use traffic stops to investigate other crimes (assuming one can call speeding a crime), stopping cars in order to ask permission to search for illegal drugs. That common practice gave birth to the phrase “racial profiling,” as troopers patrolling state highways stopped black drivers in large numbers, ostensibly for violating traffic rules but actually to look for evidence of drug offenses. Both enforcement patterns lead to the same bottom line. Because nearly all drivers violate traffic laws, those laws have ceased to function on the nation’s highways and local roads. Too much law amounts to no law at all: when legal doctrine makes everyone an offender, the relevant offenses have no meaning independent of law enforcers’ will. The formal rule of law yields the functional rule of official discretion.
... which leads to the collapse of equality in our legal system:
The criminal justice system has run off the rails. The system dispenses not justice according to law, but the “justice” of official discretion. Discretionary justice too often amounts to discriminatory justice. And no stable regulating mechanism governs the frequency or harshness of criminal punishment, which has swung wildly from excessive lenity to even more excessive severity.
The entire article is worth a read.