CHICAGO (CBS) — Gun dealers are now required to obtain licenses in Illinois after Gov. JB Pritzker signed a landmark gun control measure into law.

It’s a proposal that supporters worked 16 years to pass.

“When I first introduced a version of this bill in 2003, 16 years ago, I thought we’d be having this celebration a little bit sooner,” Illinois State Sen. Don Harmon said.

Harmon had been working just that long to pass gun dealer licensing. As of Thursday his proposal is law.

“The reason for it is to deter straw purchases, so we can prevent someone from buying a gun for someone who is not legally allowed to own a gun,” Pritzker said.

But getting here took years of fighting against gun rights organizations in Springfield. Then the shootings in Sandy Hook and Parkland happened, and thousands of fed up parents and students rose up.

“Give credit to Parkland kids,” Harmon said. “After Sandy Hook, the parents and the moms said, ‘We’re not going to take this.'”

Still, even after the measure passed the state legislature, Gov. Rauner vetoed it. So state lawmakers passed it again, but this time, fearing another veto, they didn’t send it to Rauner. They waited until Pritzker won.

“I want to say to the governor, ‘Thank yo for figuring out in four days what some other people couldn’t figure out in four years,'” Mayor Rahm Emanuel said.

The new law requires gun dealers to register with the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives as well as with state police.

Gun dealers are also required to maintain an electronic inventory, provide video surveillance and staff training.

It’s an emotional milestone for Delphine Cherry, who has lost two children to gun violence, including a daughter killed 27 years ago to the day.

“I know she’s looking down on all of us and smiling, saying ‘we did it,'” Cherry said.

The Illinois Rifle Association promised a court challenge to the new law, claiming it will be a bureaucratic nightmare for gun dealers to administer.