HELENA (AP) — A judge has upheld most of the changes Montana corrections officials made to execution methods after a legal challenge by two death-row inmates, but he said a dispute over one of the drugs used in lethal injections should be decided at trial.

Montana last year changed its lethal-injection method from a combination of three drugs to two after District Judge Jeffrey Sherlock of Helena noted state law specifically called for two drugs to be used.

Corrections officials also rewrote execution protocols so that one person with medical training administers the lethal mixture and another qualified person checks the inmate’s consciousness.

No executions have been performed in Montana since the changes.

Attorneys for inmates Rodney Allen Smith and William J. Gollehon challenged the changes on multiple fronts, most of which Sherlock dismissed in Thursday’s order.

But one argument stuck — that the state’s substitute for a drug no longer available in the U.S. for executions may not be adequate.

The new procedure calls for an injection of sodium pentothal to put the inmate into a coma, followed by an injection of a paralytic agent called pancuronium bromide.

Sodium pentothal is no longer manufactured in the U.S., and it can’t be imported. The Department of Corrections said another barbiturate, pentobarbital, can be substituted for sodium pentothal.

The plaintiffs argued that pentobarbital is not an “ultra-fast-acting” barbiturate that is required by state law to be administered in executions.

Pentobarbital is fast-acting but there is a dispute about what the Legislature meant by using the words “ultra-fast-acting” and whether the drug meets that definition, Sherlock wrote, and that must be decided at trial.

Sherlock wrote that other claims raised by the plaintiffs included absurd interpretations of the law, such as requiring the two drugs in the lethal blend to be mixed together instead of administered one after the other.

Another suggestion by the plaintiffs that a one-drug execution would be more humane is ironic, Sherlock wrote, given the plaintiffs previously advocated for a two-drug procedure.

Sherlock said he is mindful of the importance of a case involving the death penalty, but he told the plaintiffs this would be the last time he addresses new claims they bring up against the state’s execution methods.

“Plaintiffs cannot keep pointing out flaws in the (methods) only to have the state correct those flaws and then be faced with a new round of complaints that could have been addressed earlier,” Sherlock wrote.