A day after a federal court stopped an execution in Alabama, an announcement by the pharmaceutical giant Pfizer could stop even more.

On Friday, the company announced it has imposed sweeping controls on the distribution of its products to ensure that none are used in lethal injections, a step that closes off the last remaining open-market source of drugs used in executions, The New York Times reported.

More than 20 American and European drug companies have already adopted such restrictions, citing either moral or business reasons.

“With Pfizer’s announcement, all F.D.A.-approved manufacturers of any potential execution drug have now blocked their sale for this purpose,” said Maya Foa, who tracks drug companies for Reprieve, a London-based human rights advocacy group. “Executing states must now go underground if they want to get hold of medicines for use in lethal injection.”

The increasing difficulty in obtaining lethal drugs has already caused states to scramble for supplies. The Alabama Legislature attempted in 2015 to pass legislation protecting the purchase of those drugs from the public record process. There also was some discussion of reinstating the electric chair.