For the International Church of Cannabis in Denver, there were three reasons to celebrate on Thursday.
First, it was opening day. The church, a more than century-old building recently adorned with brightly colored paintings by the artists Kenny Scharf and Okuda San Miguel, welcomed the public early in the afternoon, at which time no cannabis consumption was allowed inside.
“It seemed to be a nice steady flow of people,” said Lee Molloy, a founder of the church and a member, who estimated that a couple of hundred people had come by.
Second, it was April 20, an unofficial holiday of sorts for marijuana users. There have been disagreements as to why the number 420 has taken on significance in the cannabis community, but Steve Berke, the church’s media relations director, did not want to worry about that.
And third: A challenge to the church’s legality, in the form of an amendment proposed in the state’s House of Representatives, was shut down almost as quickly as it arose on Thursday morning.
Mr. Berke and Mr. Molloy are founding members of Elevation Ministries, the religious nonprofit behind the church. “We thought we could do something different, something unique,” Mr. Berke said, explaining that the church adheres to no specific dogma.