The assault weapon the Orlando killer bought 11 days ago was a Sig Sauer MCX.

He bought it and a Glock 17 pistol legally, even though he'd been on and off the FBI watch list for suspected terrorists twice. The last time was in 2014.

What's more -- under current law, had he actually been on the watch list or even the smaller no-fly list at the time of his purchase, no law would have automatically stopped him from making a purchase.

That's because right now the laws bar felons, fugitives, illegal immigrants or juveniles, for example, from buying guns -- but not suspected terrorists.

FBI data show that people who were on the terror watch list last year were involved in background checks 244 times, and in 223 of those cases the firearm purchases went ahead. That's a 91 percent approval rate.

Now in the aftermath of Orlando, both presumptive presidential nominees are talking about toughening the laws.

"If you're too dangerous to get on a plane, you're too dangerous to buy a gun," Hillary Clinton said.

And Donald Trump tweeted that when he next meets with the National Rifle Association, he'll talk about "not allowing people on the terrorist watch list or the no fly list to buy guns."

In Congress, Senator Chris Murphy launched a filibuster to force a vote on gun control legislation.

"I've had enough of the ongoing slaughter of innocents," he said, "and I've had enough of inaction in this body."

Some in Congress worry that law-abiding citizens on the list by mistake would be blocked from buying protection. And yet, of 323 million Americans, there are just 25,000 on the watch list and 6,400 on the no-fly list. So cases of mistaken identity would involve a small portion of the population.

But there is another concern voiced by FBI director James Comey that if a suspected terrorist is blocked from buying a weapon, it might tip him off that the FBI is on his trail.