The Tennessee Supreme Court has postponed execution dates for four inmates, effectively halting all executions while the courts decide whether current protocols for putting people to death are constitutional.

Tennessee last executed a prisoner in 2009. Since then, legal challenges and problems obtaining lethal injection drugs have stalled new executions.

In 2013 and 2014, the state tried to jump-start the process with a new lethal injection method and the reinstatement of electrocution as a backup. The court set new execution dates for 11 inmates. One inmate died in prison, and the execution dates for the others have been postponed as they approach because of legal challenges to the new methods.

On Friday, the court postponed the last of the scheduled execution dates. It will set new dates after the legal questions are settled.

Attorneys for death row inmates have been trying to force the state to hand over the names of the people on the execution team, including the pharmacist who will prepare the lethal injection drug, to determine whether those people are properly qualified. However, last month the high court ruled that the state does not have to turn over those names.

Before lawmakers passed a law making electrocution a viable backup option if the proper drugs could not be obtained, prisoners could not be forced to die by the electric chair. They were, however, allowed to choose it under some circumstances.

Execution drugs have been in short supply because manufacturers have refused to sell the drugs to prisons for use in executions. Prison officials across the U.S. turned to compounding pharmacies instead, but those versions have also become difficult to come by because pharmacists are reluctant to expose themselves to possible harassment.