Last week, Attorney General Jeff Sessions retracted an Obama-era guidance to state courts that was meant to end debtors’ prisons, where people who are too poor to pay fines are sent. This practice is blatantly unconstitutional, and the guidance had helped jump-start reform around the country. Its withdrawal is the latest sign that the federal government is retreating from protecting civil rights for the most vulnerable among us.

The Justice Department helped shine a light on the harms of fine and fees when it investigated Ferguson, Mo., three years ago after the killing of the teenager Michael Brown by a police officer. As one of the lawyers on that case, I saw firsthand the damage that the city had wrought on its black community.

Ferguson used its criminal justice system as a for-profit enterprise, extracting millions from its poorest citizens. Internal emails revealed the head of finance directing policing strategy to maximize revenue rather than ensure public safety. Officers told us they were pressured to issue as many tickets as possible.

Even the local judge was in on it, imposing penalties of $302 for jaywalking and $531 for allowing weeds to grow in one’s yard. He issued arrest warrants for residents who fell behind on payments — including a 67-year-old woman who had been fined for a trash-removal violation — without inquiring whether they even had the ability to pay the exorbitant amounts. The arrests resulted in new charges, more fees and the suspension of driver’s licenses. These burdens fell disproportionately on African-Americans.

At the time of our investigation, over 16,000 people had outstanding arrest warrants from Ferguson, a city of 21,000. Untold numbers found themselves perpetually in debt to the city and periodically confined to its jail.

These problems were not unique to Ferguson. A Georgia woman served eight months in custody past her sentence because she couldn’t pay a $705 fine. A veteran battling homelessness in Michigan lost his job when a judge jailed him for bringing only $25 rather than the required $50 first payment to court. A judge in Alabama told people too poor to pay that they could either give blood or go to jail.

In 2015, the Justice Department convened judges, legislators, advocates and affected people to discuss this problem and devise solutions. Participants repeatedly asked the Justice Department to clarify the legal rules that govern the enforcement of financial penalties and to support widespread reform.

And so we did. Relying on Supreme Court precedent from over 30 years ago, the 2016 guidance set out basic constitutional requirements: Do not imprison a person for nonpayment without first asking whether he or she can pay. Consider alternatives like community service. Do not condition access to a court hearing on payment of all outstanding debt.

The Justice Department also provided financial resources to the field. It invested in the efforts of a national task force of judges and court administrators to develop best practices. And it created a $3 million grant program to support innovative, homegrown reforms in five states.

Along with private litigation and advocacy, these efforts have helped drive change around the country. Missouri limited the percent of city revenue that can come from fines and fees and announced court rules to guard against unlawful incarceration. California abolished fees for juveniles and stopped suspending the driver’s licenses of people with court debt. Louisiana passed a law requiring that judges consider a person’s financial circumstances before imposing fines and fees. Texas, where the court system’s administrative director said the guidance “was very helpful and very well received by the judges across the state,” issued new rules to prevent people from being jailed for their poverty. The American Bar Association endorsed the Justice Department’s guidance, and the Conference of State Court Administrators cited it in a policy paper on ending debtors’ prisons.

To justify reversing guidance that has had so much positive impact, Mr. Sessions asserts that such documents circumvent the executive branch’s rule-making process and impose novel legal obligations by fiat. Nonsense. The fines and fees guidance created no new legal rules. It discussed existing law and cited model approaches from local jurisdictions. The document also put state-level actors on notice that the department would take action to protect individual rights, whether by partnership or litigation.

Viewed in that light, the true intent of Mr. Sessions’s decision comes into focus. Sessions pulled 25 guidance documents last week. Sixteen of those involved civil rights protections — including 10 related to the Americans With Disabilities Act and one on the special harms that unlawful fine and fee practices can have for young people. Withdrawing these documents is consistent with the Trump administration’s hostility to civil rights in a host of other areas: abandoning oversight of police departments, reinterpreting anti-discrimination statutes to deny protection to L.G.B.T. individuals and switching sides in key voting rights cases.

The push to abolish debtors’ prisons will continue, as community advocates and local officials press on. It would be preferable, of course, for the federal government to fulfill its role as a leading protector of basic constitutional rights. Unfortunately, Mr. Sessions has made clear that under his leadership it will not.

Politicians often escalate drug war rhetoric to show voters that they are doing something. But it is rare to ignore generations of lessons as President Trump did earlier this month when he announced his support for the execution of drug traffickers.

This idea is insane. But the war on drugs has never made any sense to begin with.

Executing a few individual smugglers will do little to stop others because there is no high command of the international drug trade to target, no generals who can order a coordinated surrender of farmers, traffickers, money launderers, dealers or users. The drug trade is diffuse and can span thousands of miles from producer to consumer. People enter the drug economy for all sorts of reasons — poverty, greed, addiction — and because they believe they will get away with it. Most people do. The death penalty only hurts the small portion of people who are caught (often themselves minorities and low-level mules).

Indeed, on the ground, the threat of execution will even help those who aren’t caught because they can charge an increased risk premium to the next person in the smuggling chain. The risk of capture and punishment increases as drugs move from farm to processing lab, traversing jungles, through cities, across oceans, past borders, distributed by dealers and purchased by consumers. The greater the risk to smugglers in this chain, the more they can demand in payment.

Without the drug war, substances like cocaine, heroin, marijuana and meth are minimally processed agricultural and chemical commodities that cost pennies per dose to manufacture. But lawmakers have invented a modern alchemy called drug prohibition, which transforms relatively worthless products into priceless commodities for which people are willing to kill or die.

The kind of get-tough measures that may give one country leverage against another have little effect among individual actors who need only to move drugs through their own segment of the supply chain. Indeed, by making the drugs ever more valuable, they have only amplified the motivational feedback loop of the very people lawmakers are trying to stop.

An overreliance on intensive policing over the decades has also produced a rapid Darwinian evolution of the drug trade. The people we have typically captured tend to be the ones who are dumb enough to get caught. They may have violated operational security, bragged too much, lived conspicuous lifestyles or engaged in turf wars. The ones we usually miss tend to be the most innovative, adaptable and cunning. We have picked off their clumsy competition for them and opened up that lucrative economic trafficking space to the most efficient organizations. It is as though we have had a decades-long policy of selectively breeding supertraffickers and ensuring the “survival of the fittest.”

To support his case for executions, Mr. Trump cites draconian penalties in other countries. Iran has used the death penalty extensively in drug cases, but more than 2.8 million Iranians still consume illicit drugs. Earlier this year, the Iranian government even repealed the use of executions in most drug cases which could spare up to 5,000 people on death row.

Mr. Trump often praises President Rodrigo Duterte’s brutal drug war in the Philippines, which has claimed 12,000 to 20,000 lives in mostly extrajudicial killings. But there is little indication that drug use has actually decreased. In fact, as the killings have increased, so too have the government’s drug use estimates. What began as 1.8 million users at the beginning of 2016 grew to three million and later four million. Last September, the Philippine Foreign Secretary, Alan Peter Cayetano, even raised that estimate to seven million. The higher numbers are likely inflated, but more killings do not appear to reduce the number of users.

Singapore notoriously refuses to publish reliable drug-use statistics, so there is no way to show whether executions have any measurable effect on drug consumption. As Harm Reduction International pointed out, however, Singapore’s seizures for cannabis and methamphetamine increased 20 percent in 2016 while heroin seizures remained stable. Moreover, 80 percent of Singapore’s prisoners are incarcerated for drug-related offenses. All of this suggests, Singapore’s famous panacea to solve the drug problem is not as miraculous as it seems.

Mr. Trump also cited his border wall as a way to reduce overdoses. In the unlikely event that the wall puts a significant dent in heroin smuggling, it could actually cause overdoses to skyrocket in this country because it would give dealers an incentive to adulterate remaining heroin supplies with even more fentanyl to stretch their profits. Fentanyl is more compact, much easier to obtain and dramatically more potent.

Mr. Trump is not advancing a new strategy to deal with opioids. It was President Clinton who put these death penalty statutes on the books as part of the 1994 crime bill, but they remain unused. Mr. Trump and Attorney General Jeff Sessions are trying to change that. They want to use those laws in racketeering cases and ones involving large quantities of drugs even though the Supreme Court has ruled that capital punishment should be reserved only for crimes resulting in death.

The Donald Trump of 2018 should take a lesson from the Donald Trump of 1990 when he told the Miami Herald: “We are losing badly the war on drugs. You have to legalize drugs to win that war.”