At this week’s G-20 meeting in Australia, British Prime Minister David Cameron outlined his proposed restrictions on speech as a mechanism for combatting terrorism and youth radicalization at home.

Cameron told the Parliament the root cause of extremism was not poverty, social isolation from the mainstream or foreign policy.

“The root cause of the challenge we face is the extremist narrative. So we must confront this extremism in all its forms,” Cameron said.

“We must ban extremist preachers from our country. We must root out extremism from our schools, universities and prisons[.]”

This is the wrong answer.

Youth “radicalization” is a part of growing up as children test boundaries, learn more, test more boundaries, and so on. It’s how they learn initiative and individual responsibility.

“Extreme” speech also is a way of pushing boundaries. More importantly, it’s a way of drawing the public’s and government’s attention to this or that problem, and of pushing authorities to take corrective action—where appropriate. The public, after all, is fully capable determining for itself whether the problem described really is worth any hoo-raw.

Most importantly, though, it’s an extremely dangerous thing for government to limit speech or radical behavior. What’s the limiting principle for such limits? In what way government draw the line here, and not one syllable further? In what way can government say this is too radical, but that is not? In what way can government discriminate incitement to riot from a misunderstood speech?

“I know it when I see it,” as a Supreme Court Justice said about pornography, is a poor standard, and it leaves the matter open to government abuse. If this speech is too extreme, then what about that speech? And the next speech? Absent a clearly stated limit—and Cameron appears to have offered none—there’s nothing to keep government from adding limits, extending them, barring, for instance, criticism of government as prejudicial to good order.

No, a better answer is to let the speech fly, let the “radicalization” occur. Give parents and schools the tools to teach better (which begins with holding the parents accountable for their failure to be parents). Let the “radicalized” go join the terrorists overseas—don’t let them come back. Punish the domestic crimes when they occur, don’t make additional crimes through legislation. There is already a sufficiency (and perhaps too many) conspiracy laws on the books which can be used to preempt domestic crime and terrorist activities; enforce these, don’t create more conspiracy crimes legislatively.

Cameron’s proposal is disappointing from the leader of the birthplace of John Locke.