A key piece of legislation that will pave the way to a legal cannabis economy in the United States could pass as soon as 2019, Kevin Murphy, the founder, chairman and CEO of Acreage Holdings, told CNBC on Thursday.

"We believe it's not necessarily an if, but a when, and I believe it's not within the next couple of years. I believe it takes place in 2019," Murphy told Jim Cramer in an exclusive "Mad Money" interview.

Murphy was referring to the STATES Act, a bipartisan bill crafted by Sens. Cory Gardner and Elizabeth Warren. An acronym for "Strengthening the Tenth Amendment Through Entrusting States," the bill would pave the way for U.S.-based cannabis businesses like Acreage to run their operations legally, have accounts at federally regulated banks and list on U.S. stock exchanges if passed.

Murphy said that the passage would also mark the start of a cannabis industry migration to the U.S. market.

"All of these companies today are headed to Canada. Canada is one-tenth the size of the opportunity here in the U.S., and we all know the prize is here," he said, adding that passing the act would lead to "big investment [and] big conglomerates coming back to the U.S."

Acreage Holdings made headlines in April when former Republican House Speaker John Boehner said he would join its board of directors, saying that his views on cannabis "evolved" as he learned more about its benefits.

Boehner isn't the only big name on Acreage's board. In recent months, the company has added the former CEO of Time Warner Telecom, former CFO of IBM and former prime minister of Canada to its upper ranks.

Those leaders, particularly the politicians, have "afforded [Acreage] great success" as the company expands its U.S. footprint, which has grown to 19 states, Murphy said.

"They can make a phone call, and they get accomplished, in that phone call, [something] that would've taken me six months to get done prior to that," the CEO said, adding that his positive outlook on the U.S. cannabis space stems from the notion that it "is one of the only bipartisan issues in Washington today."

Acreage Holdings is a cannabis investment company that describes itself as having "among the most diverse portfolios of cultivation, processing and dispensing operations in the U.S." The New York-based operator went public on the Canadian Securities Exchange in mid-November having raised more than $314 million ahead of the debut.

On the company's website, its stated mission "is to become the world's leading cannabis company, bringing safe, affordable cannabis to everyone who needs it."