Justice Kagan explains in her dissent:
To justify such religious discrimination, the State must show that its policy is narrowly tailored to a compelling interest. I have no doubt that prison security is an interest of that kind. But the State has offered no evidence to show that its wholesale prohibition on outside spiritual advisers is necessary to achieve that goal. Why couldn’t Ray’s imam receive whatever training in execution protocol the Christian chaplain received? The State has no answer. Why wouldn’t it be sufficient for the imam to pledge, under penalty of contempt, that he will not interfere with the State’s ability to perform the execution? The State doesn’t say. The only evidence the State has offered is a conclusory affidavit stating that its policy “is the least restrictive means of furthering” its interest in safety and security. That is not enough to support a denominational preference.