you will see that there are not checkpoints and gates, travel between states happens readily and easily. That's why it is useless to talk about any particular state's gun laws. They are largely symbolic.

especially handguns in other states.
https://en.wikipedia.org/wiki/Gun_Control_Act_of_1968

It is actually a federal crime for me to buy a handgun in Arizona or sell one to a resident of any other state without the gun being shipped to a licence dealer in their state.

Machine guns are illegal in every state in France, in fact every country in the EU, but that didn't stop the several mass shootings in Paris did it? Or someone with an automatic weapon shooting up a Copenhagen bar, or an art gallery in Brussels.

For all we know, they had automatic weapons. I don't know. If they did, the OP and any discussion on gun control is moot.

There's no stopping someone who is determined to kill in their religion's name. They'll find a way. Once a person decides to step outside the boundaries of the law they have quite a few options that aren't on the table for the regular law-abiding citizen.

Drugs like heroin and meth are illegal in every state. I'd venture to say you wouldn't have much trouble finding all you want within a day or two if you really wanted some.

The problem goes much deeper than passing a few more laws in this case. We're dealing with people who are quite prepared to die for their cause.

Theres no way terrorists could get guns in brady 'A' rated CA.