States that impose the death penalty have been facing a crisis in recent years: They are short on the drugs used in executions.

In California, which has the country's largest death row population, the chief justice of the state supreme court has said there are unlikely to be any executions for three years, in part due to the shortage of appropriate lethal drugs. As a result, state prosecutors are calling for a return of the gas chamber.

Ohio, which is second only to Texas in the number of executions carried out since 2010, said it will run out of the drug it uses in executions, pentobarbital, on Sept. 30. The state has two men scheduled for execution in November, and eight more set to be killed after that. Every state's supply of pentotbarbital, which has been the principal execution drug, expires at the end of November.

The shortage has forced death penalty states to scramble on two fronts: They are hunting for new suppliers or different drugs to use, and enacting changes to public records laws to keep the names of suppliers and manufacturers of those alternative drugs secret.

The lack of lethal drugs, and the fight over keeping new ones secret, are partly the result of a remarkably effective campaign by opponents of the death penalty, who have, in effect, taken their efforts from the court room to the boardroom.

Each time a state has found a new source for a drug to use in executions, Reprieve, an anti-death penalty organization based in London, in collaboration with death penalty lawyers in the United States, has used freedom of information laws, the local news media and the powers of persuasion to compel the drug's manufacturer to cut off the supply.

"Who's easier to persuade? The Supreme Court or a corporation that has financial interests?" said Clive Stafford Smith, a British-American, who was a death penalty lawyer in the South for many years before founding Reprieve. "You can make it not worth their while to allow their drugs in executions."

The effectiveness of Reprieve's campaign might well be behind the action taken last year by the state of Texas, which leads the nation in executions.

When a reporter for the Austin American-Statesman, Mike Ward, using the state's Public Information Act, sought information about the drugs used in executions, the Texas Department of Criminal Justice fiercely resisted.

In one legal filing, Patricia Fleming, the agency's assistant general counsel, said revealing the information about the drugs and who made them would invite "financial intimidation and negative publicity," as well as "intensive lobbying" and "unrestrained harassment." Referring to death penalty opponents, Fleming asserted that "essential to their strategy is knowledge of the private companies" that supply the drugs used in lethal injections.

The state attorney general ruled against her, and the department disclosed that it had enough pentobarbital at the time for 23 executions, Ward reported.

Death penalty states are now taking measures to keep anti-death penalty activists, and journalists, from learning the identity of suppliers. A Georgia law enacted in March provides that any information about a "person or entity that manufactures, supplies, compounds, or prescribes the drugs, medical supplies or medical equipment" used in an execution shall be considered a "confidential state secret." Already this year, at least three other states — Arkansas, South Dakota and Tennessee — have amended their public records laws to exempt the names of suppliers from disclosure.

Lethal injection was first proposed as a method of execution in the 19th century by a New York doctor who argued it would be cheaper than hanging. It took 100 years or so for it to be used, but every state that set out to execute people eventually adopted it as the chosen method.

Generally, states have used a three-drug protocol. The first was an anesthetic, sodium thiopental, intended to render the prisoner unconscious so that he or she does not experience the pain and suffering from the drugs to come. The second drug, pancuronium bromide, paralyzes the diaphragm and lungs, making it impossible for the condemned to breathe. Finally, potassium chloride is injected, causing death by cardiac arrest.

In 2008, the Supreme Court, in Baze v. Rees, held that lethal injection did not run afoul of the Eighth Amendment proscription on "cruel and unusual punishment."

But the Court recognized care had to be taken in the killing, so that it wasn't unconstitutionally "cruel." The most critical drug, it emphasized, is the anesthetic.

"It is uncontested that, failing a proper dose of sodium thiopental that would render the prisoner unconscious, there is substantial, unconstitutionally unacceptable risk of suffocation from the administration of pancuronium bromide and pain from the injection of potassium chloride," Chief Justice John Roberts wrote.

The problems for death penalty states, and the opening for opponents of the death penalty arose when the only company that had governmental approval to make the anesthetic, Hospira, announced in 2011 that it was suspending production because of manufacturing problems at its plant in North Carolina.

Arizona, with two executions pending in late 2011, managed to find another source of sodium thiopental; but it didn't want the public to know what it was or where it came from.

When lawyers for Jeffrey Landrigan, one of the men facing death, sought the name of the supplier, Arizona's state attorney general refused to say. Ultimately, on the eve of Landrigan's execution, the attorney general disclosed that the drug had come from Britain. He did so, he said, to allay fears that the drugs had been made in a Third World country and might be contaminated and unsafe.

Tennessee also acknowledged that one of its execution drugs had been made in Britain but refused to divulge the company's name.

At Reprieve, Maya Foa, head of the lethal investigation project, searched through medical and pharmaceutical directories to identify British companies that made sodium thiopental.

The British company selling sodium thiopental to Arizona, Tennessee and other states turned out to be a tiny wholesaler that operated out of the back of a driving school in a working class neighborhood in West London.

It was called Dream Pharma, and it was basically a one-man operation. It also suddenly became more profitable, as states in America moved to improvise. Stafford Smith, Reprieve's director, wrote a letter to Dream Pharma.

"You have played a significant role and hold responsibility for the potential deaths of many people in the United States," he wrote.

Reprieve sent the letter, along with Dream Pharma's address and phone number, to journalists, and articles appeared in British newspapers and on the BBC. Dream Pharma shut down. The company has declined to comment on its battles with Reprieve or the sale of drugs to the U.S. for executions.

Reprieve then successfully lobbied the British government to ban exports of any drugs to the U.S. for executions. Capital punishment for murder was abolished in Britain in the early 1960s even though polls showed the public supported it.

With Hospira out of the business, states had become fairly desperate. That urgency was captured in government emails and documents obtained by death penalty defense lawyers.

"I have been given a task to obtain some Sodium Pentothal by any means available," the director of the pharmacy in the Nebraska department of corrections wrote to her counterparts in several states. "Does anyone know where I might start looking?"

She eventually found a small wholesaler in Mumbai, India, which operated out of two rooms on the ground floor of an apartment building; it had no air conditioning, raising doubts about the safety and efficacy of any drugs stored there.

Reprieve again went to work, alerting local reporters and holding a news conference in Mumbai. Officials from India's food and drug administration raided the offices. The company was quickly out of business.

In California, prison officials turned to hospitals throughout the state in search of sodium thiopental, without success. The warden at San Quentin explored buying some in Pakistan.

In the end, Arizona officials solved California's problems, supplying 12 grams of sodium thiopental from its limited supply, a happy exchange according to government emails unearthed by death penalty opponents.

"You guys in AZ are life savers," a California corrections officer wrote to his Arizona counterpart. "Buy you a beer next time I get that way."

Some death penalty states, looking to solve their drug supply problems in a more reliable way, switched drugs — opting for pentobarbital, an anesthetic commonly used in putting animals to sleep. The first state to use it for an execution was Oklahoma, in December 2010, and it quickly became one of the execution drugs of choice.

This time, however, Reprieve was not up against a small entity. Only one company had government approval to sell pentobarbital in the U.S., and it was a major international pharmaceutical company, Lundbeck Inc. Headquartered in Denmark, it had some 6,000 employees worldwide; its American plant was in Kansas.

When Reprieve approached Lundbeck, in early 2011, the company said it was "adamantly opposed" to its drugs being used in executions — its primary use is in the treatment of epilepsy — but it said it had no control over what happened after its products were sold to wholesalers or distributors.

Reprieve ratcheted up the pressure. Every time Lundbeck's pentobarbital was used in an execution, it issued a press release.

Anti-death penalty activists campaigned against Lundbeck on Twitter and Facebook, shareholders raised questions at the company's annual meeting, a pension fund sold its shares, and the company's place on an annual ranking of Denmark's best companies fell from 17 to 40.

Lundbeck then did what it had said it couldn't do: It devised a distribution system that would keep its pentobarbital from the states that conducted executions.

Last month, Hospira announced that it was putting controls in place so that three of its drugs — pancuronium bromide, potassium chloride and propofol — would not be used in executions.

Once again, that has left states trying to figure out what to do. In Colorado, a man who killed three teenagers and their boss in a pizza restaurant in 1993 is set to be executed in August. But the state does not have the proper drugs, causing the director of prisons to send an urgent plea to the state's compounding pharmacies. At "compounding pharmacies," pharmacists mix, or compound, the ingredients for drugs on site.

Last October, South Dakota became the first state to use a compound drug in an execution, and it did so twice.

Lawyers for one of the men to be executed, Robert Moeller, who had kidnapped, raped and murdered a 9-year-old girl, filed a lawsuit to obtain information about the supplying pharmacy. The state resisted, and a federal judge sided with the state.

South Dakota was among the states to recently pass a law exempting the names of suppliers of lethal injection drugs from its public records law. The change was necessary, said South Dakota State Sen. Jean Hunhoff, "because there's been harassment that has occurred against non-protected manufacturers and pharmacists, thereby causing difficulty for the state in obtaining the necessary chemicals for the lethal injection."

South Dakota's law passed in the state senate without opposition, and the house by a lopsided 60-8.

Raymond Bonner, a lawyer and former New York Times reporter, is the author of "Anatomy of Injustice: A Murder Case Gone Wrong."