"The bill opens the market back up," said Evan McMahon, of the advocacy group Hoosier Vapers, who says last year's law dropped the number of in-state manufacturers from 60 to single-digits. "It will allow companies to come back home."

First approved in 2015, Indiana's vaping law was ostensibly designed to create "e-liquid" safety standards. But changes made to it last year effectively gave a Lafayette-based security firm, Mulhaupt's Inc., sole discretion to decide who could be certified to produce "e-liquid" sold in the state.

Mulhaupt's certified only a handful of producers.

"We had people who could do this safely and we told them 'You're not allowed to be in the business,'" Head said.

The law guided everything from requirements for sinks to the details of contracts with outside security firms and the qualifications of those firms' personnel. Facilities had to be continuously monitored by video. And manufacturers needed an assortment of security certifications that few U.S. companies, if any, besides Mulhaupt's were qualified to provide.

By summer, the FBI was questioning a number of people connected to the law, including legislators who were instrumental in its passage such as Republican Sen. Ron Alting, who represents the district where Mulhaupt's is based.