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 says 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 Ronald Allen Smith and William 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.