“Here we have an entirely new opportunity,” said Alejandro Gaviria, Colombia’s health minister, whose agency is issuing the licenses.

Mr. Gaviria said that decades of efforts by Colombia to move drug cultivators to other crops had hit a wall: The peasants made less money, rural development moved backward, and some farmers simply returned to drug cultivation.

“It’s been a complete failure,” he said.

Now, Mr. Gaviria argued, legal drugs could become an important economic tool for postconflict Colombia.

More than 220,000 people were killed as the rebels of the Revolutionary Armed Forces of Colombia, or the FARC, waged 52 years of war against paramilitary groups and the government, displacing the state entirely in some places. In the final decades, guerrillas moved into narcotics, financing the conflict through taxes on marijuana and cocaine, government officials and experts say.

The logic now: What if those profits were put into the hands of the government and peasants instead?

There is also a third actor that will profit greatly from the newly legal business, Canada’s PharmaCielo. Others, including a Colombian company, are seeking licenses, but PharmaCielo is the most prominent in pursuing cultivation in areas once controlled by the rebels.

Formed in 2014 as the new law was taking shape, PharmaCielo is already testing strains of cannabis more potent than those the rebels ever controlled. Its directors include former executives of Philip Morris and Bayer. The company sees a future in which the legal drug industry is controlled by the same kind of multinational corporations that the Marxist-Leninist guerrilla movement aimed to drive from the country.