If you browse the website of Law Enforcement Against Prohibition (LEAP), you will notice a conspicuous theme: The war on drugs is corrupting America's cops.

LEAP, a group of current and former cops, prosecutors, and judges who oppose the drug war, lists "police corruption and misconduct" as one of the four main topics covered by its speakers. The profile of former Portland, Oregon, Det. Donald Dupay, for example, says he "witnessed the unintended consequences of the war on drugs that caused some of the officers in his department to become corrupt." The profile of former Oakland, California, prosecutor James Anthony says his opposition to drug prohibition stems in part from observing "the negative impact of the 'War on Drugs' on the integrity of the police force." The profile of Fred Martens, a former undercover narcotics cop with the New Jersey State Police, says he saw the drug war "corrupt innumerable law enforcement officials."

The list of law enforcement officials corrupted by the drug war is a long one. Here are some stories from just the last few weeks:

• Two Philadelphia cops pleaded guilty to federal charges stemming from their plan to steal heroin from a suspected drug dealer.

• A former deputy with the Harris County, Texas, Sheriff's Department pleaded guilty to extortion charges after stealing two kilograms of fake cocaine during a federal sting operation.

• A New York City detective was convicted in state court of conspiring to pay off police informants with illegal drugs.

• Six San Francisco narcotics cops were accused of performing illegal searches, then covering them up with perjured testimony.

• The head of the Mesquite, Texas, anti-narcotics unit was arrested and charged with theft of government money after reports that he was stealing cash seized during drug raids.

• The head of the Contra Costa County, California, Narcotics Enforcement Team was charged with leading a conspiracy in which he and other law enforcement officials stole illicit drugs from evidence lockers and sold them on the street.

• A second police officer agreed to testify for the prosecution in the state trial of a retired judge and former prosecutor in Wayne County, Michigan, who is charged with suborning and knowingly allowing perjury by cops in drug cases.

• A former Texas district attorney, Joe Frank Garza, pleaded guilty in state court to misappropriating $200,000 in drug forfeiture funds.

Some of these stories involve public officials on the take; others are stories of cops, prosecutors, and judges who crossed a line in their zeal to fight the drug war. But I'm not sure there's much difference. In fact, one reason drug cops may be so susceptible to corruption is that the legal tactics they use to enforce the drug laws are so ethically dubious.

Morally, it is not much of a leap from legal asset forfeiture—in which cops take property from people who have never been charged with a crime, sell it, and use the proceeds for their department's budget—to simply pocketing money from suspected drug dealers. Consider what was happening in Tenaha, Texas, until recently. Cops would pull over motorists, accuse them of drug activity with little or no evidence, and give them a choice: They could sign the cash, jewelry, and other property in their possession over to the police department and be on their way. Or they could fight the charges, risk a felony conviction, spend one or more nights in a jail cell, and possibly pay more in legal fees than their property was worth.

Legal niceties are often the only distinction between civil asset forfeiture and a shakedown. It is not hard to see how cops who routinely engage in the former might grow morally complacent enough to contemplate the latter. Audio from a 2008 raid on the home of Monroe County, Michigan, resident Rudy Simpson, which hit the Internet last month, catches two state police officers deciding whether to take his recording equipment, flat-screen TV, and computers. Simpson says they also took DVDs, a camera, a gold ring, and $400 in cash. The raid, justified by an "anonymous tip" that Simpson was selling pot, netted a small bag of marijuana and half a pain pill.

Not only was the seizure of Simpson's property perfectly legal under Michigan's asset forfeiture laws; this sort of confiscation is encouraged. In 2009 The Detroit News reported that forfeitures in some Michigan jurisdictions had jumped 100 percent or more in recent years, as police departments used the procedure to supplement budgets strained by the bad economy and government debt. Police need not charge someone with a crime to take his property, and it can cost thousands of dollars to get it back. One former prosecutor told The Detroit News: "Forfeiture laws are being abused by police and prosecutors who see only dollar signs. It's a money grab, pure and simple—a sneaky way of getting a penalty on something prosecutors can't prove. It's like shooting fish in a barrel." It is not terribly surprising, then, to read that the same Lt. Luke Davis who oversaw the raid on Rudy Simpson's home was later arrested because, as the local news station WXYZ reported, "he and…others sold off drugs and confiscated goods for their own profit."

Abuse of the drug war's informant system is not hard to understand either. Informants are often drug dealers, who benefit from ratting on the competition, or addicts who tip off police in exchange for money, which they then use to purchase drugs. It is not at all uncommon for police to overlook an informant's own drug activity. In cases where the same drug informant whom police have described on search warrant affidavits as honest and trustworthy later comes forward with allegations of police corruption, the public is quickly made aware of that informant's shady history as well as the slippery nature of drug informants in general.

The Goldwater Institute, a libertarian think tank in Phoenix, recently published a report on "reverse stings" by police in Chandler, Arizona. Unlike traditional stings, in which undercover cops bring money to make a drug buy, reverse stings involve cops who arrange to sell drugs. Reverse stings are a lot more dangerous for everyone involved because police have an incentive to negotiate the largest deal possible, increasing the likelihood that their targets will come heavily armed. One Chandler bust last July ended with a dead cop, two more seriously injured, and two dead suspects. Reverse stings are trickier from an evidentiary perspective as well. Although it is clearly illegal to show up at a standard sting with a couple kilos of cocaine, it isn't necessarily illegal to be carrying a large amount of cash. But reverse stings are also more lucrative. Instead of seizing a couple hundred pounds of pot, which has no value to them, cops get to seize millions of dollars, which then flows into the police department's budget.

In a 1994 study published in Justice Quarterly, University of Tennessee criminologist J. Mitchell Miller and Middle Tennessee State University criminologist Lance H. Selva observed several police agencies that would delay making drug busts to maximize the cash they could seize, since seized cash is more lucrative for police departments than seized drugs. In the process, of course, police allowed untold amounts of illicit drugs to be sold on the streets, which seems contrary to the stated mission of the drug war.

Even day-to-day enforcement of the drug laws is rife with moral ambiguity. In New York state, for example, marijuana possession has been decriminalized. You might therefore think that a New Yorker should be able to possess a small amount of pot for his own use without fear of criminal charges. The problem is that it's still a criminal offense to display pot in public. New York City cops, in the course of "stop and frisk" pat-downs ostensibly aimed at people carrying weapons who may pose a threat, commonly ask people to empty their pockets or bags and then arrest those who, in the process of following a police officer's order, "display" the pot in their possession. Despite the decriminalization policy, the city has made some 536,000 arrests for marijuana possession, at a cost to taxpayers of at least $500 million, since 1997.

Police likewise manufacture crimes when they set up drug deals. The routine deception and betrayal involved in befriending someone, asking him for a favor, and then punishing him for helping you out would be recognized as outrageous in almost any other context. This habit of tricking people into committing drug offenses breeds an ends-justifies-the-means mentality that can lead to more brazen, less legal ethical shortcuts.

Critics of prohibition often argue that drug cops are especially susceptible to corruption because their jobs regularly bring them into contact with black-market cash and large quantities of illicit substances worth more than the average police officer makes in a year. There is something to that, but I think the problem runs deeper. Drug crimes are consensual crimes, which means there are no aggrieved victims to file a complaint. The only way to fight consensual crimes is with surveillance, informants, or undercover cops. Surveillance requires a warrant, which requires some evidence of criminal activity. The latter two options are far more common, but they require the police to break the very laws they are enforcing—or encourage someone else to do so. That creates a moral disconnect right off the bat.

Then there is the term drug war, which implies an existential struggle. In light of such rhetoric, it is not difficult to see how law enforcement officials might be led astray not by greed but by their eagerness to prosecute and imprison drug offenders. If we are indeed fighting a war, why quibble over a white lie on the witness stand or some planted evidence that helps defeat the enemy?

None of this is meant to excuse the behavior of cops gone bad. Even within the context of an unjust prohibition system, there are cops who do their jobs by the letter of the law. But we should not be surprised when some of the police officers we ask to enforce morally suspect laws day after day, year after year, eventually cross the line from actions that are unethical but legal to acts that are both unethical and illegal.

Radley Balko is a senior editor at Reason magazine.