Florida Gov. Rick Scott on Friday signed a school safety and gun reform package passed by the Florida Legislature in the wake of the Parkland mass shooting.

The National Rifle Association responded with a federal lawsuit.

Families of the victims of the shooting met with Scott in Tallahassee earlier Friday to demand he swiftly sign the $400 million package into law.

It raises the minimum age to buy an assault-style weapon from 18 to 21, implements a three-day waiting period on those purchases and includes new checks to prevent guns from falling into the hands of the mentally ill.

The National Rifle Association opposes the bill. The lawsuit the NRA filed in federal court Friday in particular takes issue with the minimum age requirement on rifles.

"Preventing a responsible 20-year-old from purchasing the best tool for self-defense will not stop a deranged criminal intent on committing a crime," the NRA said in a statement.

The NRA says the measure violates Second and 14th Amendment rights.

Some school staff can get firearm training

Critically, the bill also includes a program to allow certain highly qualified school personnel to carry guns on campus, called the "guardian" program. Scott said he doesn't support a number of items in the bill, including arming teachers.

"There are things in this bill that I oppose and I've been pretty open about that," Scott said. "I still think law enforcement officers should be the ones to protect our schools. I've heard all the arguments for teachers to be armed, and while this bill was significantly changed on this topic, I'm still not persuaded."

"I'm glad however, the plan in this bill is not mandatory," Scott continued, adding that the program will be up to local officials to implement. "If counties don't want to do this, they can simply say no."

Many Democrats are continuing to call the guardian program a poison pill that could lead to deadly racial profiling.

Meanwhile, the National Rifle Association isn't happy about Scott's move. Powerful NRA lobbyist Marion Hammer sent an email to her group's Florida supporters, saying lawmakers have given into "bullying and coercion" in passing the package.

For the students of Stoneman Douglas High School, the focus will continue to be what's not in the law: a ban on assault-style weapons like the AR-15 used in Parkland.

Chris Grady, a senior at Stoneman Douglas, called the signing of the legislation a "baby step."

"Obviously, this is what we've been fighting for. It's nowhere near the long-term solution,'' said Grady, an organizer of the March for Life later this month in Washington, D.C. "It's a baby step, but a huge step at the same time. Florida hasn't passed any legislation like this in God knows how long. It's nowhere near what we want, but it's progress and uplifting to see," he told the Associated Press.

The shooting at Stoneman Douglas happened on Valentine's Day. Former student Nikolas Cruz is charged with 17 counts of first degree murder.

The Associated Press contributed to this report. Check back for updates on this breaking news story.