A few weeks ago, fellow Post blogger Orin Kerr put up a post arguing that contrary to what you may commonly read, on Fourth Amendment cases the Supreme Court usually is as likely to rule against the government as in favor of it.

He makes a convincing argument. But I think there’s another factor we need to consider: In the real world, the decisions that uphold Fourth Amendment rights often don’t matter.

That’s because the rulings are generally difficult to enforce. The exclusionary rule is meant to help deter violations, but it only protects the guilty. And it’s far from clear that it’s an effective deterrent. For innocent people, an illegal search usually doesn’t inflict enough damage to make a lawsuit worthwhile. And even when it does significant damage, the various immunities offered to law enforcement officials and the government entities that employ them make it difficult to even get a case in front of a jury. And once you’re there, juries are inclined to side with police officers. Even if you somehow manage to win an award of damages, that money will almost always be paid by the taxpayers  who fund the government that employs the offending law enforcement officers, not the officers themselves. So there’s no real deterrent here, either.

A couple of recent stories illustrate these problems in action. First, we have a report in the Chicago Tribune looking at the use of DUI checkpoints in various counties across Illinois. The Supreme Court upheld DUI checkpoints in the 1990 case Michigan v. Sitz, finding that the value of preventing drunk driving outweighed the Fourth Amendment violations of randomly stopping motorists to see if they’re intoxicated. (The court relied on an inflated, misleading statistic about DUI deaths to reach this conclusion, but that’s another matter.) The court didn’t really consider whether checkpoints were actually all that effective at catching drunk drivers. (The Michigan Supreme Court ruled that they were not — the U.S. Supreme Court ruled that their actual empirical effectiveness isn’t the right test.) The court has struck down checkpoints for most other reasons, including to check for narcotics, expired licenses and other crimes and violations. The court found that so long as drunk driving is the primary stated reason for the checkpoint, the police can go ahead and issue other citations, should they find them.

You can probably guess what has happened since. Police departments across the country have been using the roadblocks to generate revenue from traffic offenses. They’ll claim that drunk driving is the “primary purpose,” but it’s clear from what transpires at the checkpoints that this isn’t the case. The Tribune report is only the latest of countless media outlets across the country to document this, although this time we have the added wrinkle that local police agencies are also getting hefty federal grants to run these checkpoints. The Tribune reports:

The implicit theory is that local police departments certainly would not keep taking public money to pay for safety programs that don’t work.

Except apparently they do keep taking money for this tradition, and have modest results to show for it. If you are a white driver in a white neighborhood, Chicago police almost never stop you, although the city’s minority drivers have been found to be the least likely population to be driving drunk.

Thanks to the statistical sleuths at the Chicago Tribune studying Illinois Department of Transportation data, we now know that police departments across Lake County also have staged hundreds of checkpoints, spent millions and have caught … almost no one.

During the five years in question, Waukegan police spent $478,000 to nab 890 DUIs at the local checkpoints. That’s just 12 percent of the 7,672 citations issued at those pit stops. The vast bulk of those citations are for burned out taillights, insurance lapses, unbuckled seat belts and license violations.

Further, it means Waukegan police spent $537 to ring up each DUI arrest.

By comparison, Gurnee spent much less, but also got a much quieter bang for the bucks. Gurnee spent $56,000 for 42 DUI arrests, which constituted 4 percent of the 935 total citations.

None of the 200-plus jurisdictions studied statewide came off as models of efficiency in the statistics, but Lake County was particularly pale.

The report goes on like that.

Vernon Hills? It spent $2,356 for a goose egg. No DUIs, although officers there did issue four citations for other violations . . .

Lake County Sheriff’s Department, $7,044 for 7 DUI arrests which was 6 percent of 123 citations.

South Barrington, $16,299 for 10 DUIs and 290 citations (3 percent).

Fox Lake, $11,995 for 4 DUI nabs among 212 citations (2 percent).

Lake Zurich, $50,988.58 for 76 DUI arrests, 11 percent of 807 citations.

Grayslake/Hainesville, $37,367 for 36 DUI arrests, 7 percent of 501 tickets.

Nobody did particularly well.

Sobriety checkpoints have become the most intrusive and expensive-to-run minor violation gotchas in the state.

This is precisely what the Supreme Court said that police departments couldn’t do — use checkpoints to generate revenue. Yet report after report has shown that this is exactly how they’re used.

The problem is that unless a group like the ACLU files a class action suit, no driver written up for an expired license has the time, money, or interest in filing a lawsuit. It’s also far from clear such a suit would be successful. So long as the local police department claims the primary purpose of the checkpoint is to catch drunk drivers, it’s difficult to argue otherwise. The Supreme Court is generally reluctant to question the stated intentions of government officials, particularly in law enforcement.

And so police agencies across the country continue to violate the intent of the court’s ruling in 1990. And most of them do it with funding from the federal government.

The other story involves an incident between the U.S. Customs and Border Protection and a young woman who, oddly enough, had aspirations of becoming an officer for that very agency. Jacob Sullum at Reason has the details:

Cooke was driving from Norfolk to her boyfriend’s house in Ogdensburg, the northern border of which is the St. Lawrence River. If you cross the river, you are in Canada, but Cooke was not crossing the river. She nevertheless became subject to the arbitrary orders of CBP agents by driving through one of the country’s many internal immigration checkpoints . . .

After presenting her driver’s license, Cooke, who surely learned in college that police (and even CBP agents!) need “reasonable suspicion” to detain someone, asks why she was pulled over. “You guys have no reason to be holding me,” she says. A male agent who identifies himself as a supervisor has no explanation for the detention, but he says Cooke will have to wait for a drug-sniffing dog to inspect her car. “Well, they’d better be here soon, because if not, I’m calling 911, and this can all be figured out,” Cooke says. “You guys are holding me here against my will.” Eventually the female agent who first interacted with Cooke says she seemed nervous—an all-purpose excuse for detaining someone, since people tend to be nervous when confronted by armed government officials.

“Why do you want to get in my trunk when you have no right to?” Cooke asks. That question also reflects a potentially disquieting familiarity with Supreme Court decisions related to traffic stops. Just last month, the Court ruled that, in the absence of reasonable suspicion, police may not extend a traffic stop for the purpose of walking a drug-sniffing dog around the vehicle. But the Court also hassaid that if a dog alerts to a car (or, same thing, a cop claims that the dog alerted), that is enough by itself to supply probable cause for a search, even though there are lots of reasons (including a handler’s deliberate or subconscious cues) why a dog might alert to a car that contains no contraband.

“If they’re not here within 20 minutes, I’m gone,” Cooke says. “You can leave,” the male agent says. “You can walk down the road right now….Your car’s not going anywhere….I’ll spike the tires.”

Cooke and the agent eventually get into an argument about where she’s supposed to stand, which ends with her on the ground writhing in pain after getting shot with a stun gun.

As Sullum points out, this case is especially relevant because not only did the agents violate Cooke’s Fourth Amendment rights, but also Cooke told them they were violating their rights at the time. Not only did they go ahead and detain her anyway, but also it seems likely that her insistence on asserting her rights is what got her shot with a stun gun.

There’s often a heightened contempt among cops for people who know and assert their rights. The more you cite Supreme Court cases to assert your right during an interaction with law enforcement, the more likely you are to wind up with your face on the pavement. (That contempt doesn’t just come from cops — Sullum notes the quote from a local resident interviewed by a local paper about the Cooke incident: “If you have nothing to hide, why be a jerk? Just cooperate.”)

This seems perverse. Not only do Supreme Court rulings not prevent law enforcement officials from violating our rights, but also any attempt to use the rulings to defend your rights makes it more likely that you’ll get a violent reaction from law enforcement.

Cooke has a better chance of winning a lawsuit than any of those Illinois drivers hit with traffic fines at a DUI checkpoint, but her lawsuit is far from a sure thing. And again, even if she wins, it’s unlikely that the agents in question will suffer any consequence. In fact, if those agents are disciplined, it will most likely be because Cooke recorded her interaction with them and was able to generate some media coverage, not because the government agency that employs them was proactively enforcing the Fourth Amendment. (As Sullum points out, the only legal action currently under consideration at present is against Cooke.)

When it comes to the Fourth Amendment, the law as it’s laid out in Supreme Court opinions is often quite a bit different than the law on the ground.