INDIANAPOLIS — On the altar, behind a row of flickering candles, the silhouette outline of a marijuana leaf shined in lights. 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?

“We will celebrate life’s great adventures,” Mr. Levin said before the service, as clumps of uniformed police officers began gathering outside the newly renovated church, front and back. “This is not just smoking pot and getting high. It’s about the birth of a new religion. I’m a smile harvester.”