Colored balloons occasionally bounced through the air as the minister of music led a band in a pew-shaking rendition of "Mary Jane," the funk tribute to the drug. And Bill Levin, who was introduced as "the Grand Poobah" of this new church, finished the gathering with a simple message: "Light up, folks!"

As legislation that proponents call a religious freedom law took effect in Indiana on Wednesday, Mr. Levin's First Church of Cannabis held its first service in a quiet neighborhood on this city's Eastside. Mr. Levin, who is 59 and known around here for his wild puff of white hair, dreamed up the church as a way to test the state's new, much-debated law: If the law protects religious practices, he figured, how could it not also permit marijuana use — which remains illegal here — as part of a broader spiritual philosophy?