User blog comment:B214/Question & Answers 5/@comment-66.87.83.231-20150427045314/@comment-26209278-20150427073327

Yes, they have to be worthy to use it. Anyone can lift it, but cannot access its divine power.

Like with Issei, he could lift it (in BB) and flow his aura into it, but could not access it's power until he was worthy (blessed by Chichigami), or if they had a pure heart (which Issei definetly didn't have)