The internet is a powerful tool for good as well as evil. So like almost every organization, ISIS has used it to organize and to spread its message. And Donald Trump wants to put a stop to that.

"We're losing a lot of people because of the internet, and we have to do something," Trump said at a rally earlier this month. "We have to go see Bill Gates and a lot of different people that really understand what's happening. We have to talk to them maybe in certain areas closing that internet up in some way."

He returned to that theme in last night's Republican primary debate: "We should be using our brilliant people — our most brilliant minds to figure a way that ISIS cannot use the internet."

When pressed on this point by Wolf Blitzer, Trump stuck to his guns: "I would certainly be open to closing areas where we are at war with somebody. I sure as hell don't want to let people that want to kill us and kill our nation use our internet."

Of course, the internet is not organized into "areas" that can be switched on and off. The internet was deliberately designed to be a globally integrated network, with everyone on the planet having access to content anywhere in the world — something our "brilliant people" would have told Trump if he'd actually asked any of them.

Chinese-style internet censorship wouldn't be effective against ISIS

Of course, if we really wanted to exclude ISIS from the US internet, there is a model of how to do it: China's Great Firewall. That's the censorship regime the Chinese government uses to try to keep subversive ideas like democracy and human rights out of their country. In principle, we could adopt the same tactics here in the United States, building a virtual wall around the United States and filtering all of the information flowing in and out of the country to try to prevent jihadists from communicating with Americans.

And for this to work, we'd have to not only prevent ISIS members from posting on US websites but also prevent impressionable Americans from browsing websites the US government deems too ISIS-friendly. This would, of course, be a massive violation of the First Amendment, and Americans are unlikely to stand for the US government deciding which websites they're allowed to read.

The Chinese experience also suggests this wouldn't work very well. Chinese elites routinely use technologies like virtual private networks to circumvent the Great Firewall. In fact, it's believed that the Chinese government has a de facto policy of tolerating the use of VPNs by the most sophisticated users, as a way of keeping those elites happy.

Some experts believe that China's Great Firewall has been effective at giving the Chinese government power over the information consumed by ordinary Chinese people, most of whom don't use VPNs. But this strategy wouldn't work very well against ISIS, which certainly has the money and know-how to invest in VPN technology. And it would be a bad idea to discard our free speech principles in a likely futile effort to stop communication between ISIS and Americans.