Conservative author Mark Steyn said the reported hundreds of Britons who have traveled abroad to train with ISIS and returned home should be tried for treason.

"I'm old-fashioned enough to believe in treason," Steyn, a "Rush Limbaugh Show" guest-host, said.

Steyn said that there are as many as 3,500 people in the United Kingdom who are being surveilled for possible ties to extremist groups.

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He compared that number to the 850 being watched during the height of the Irish Republican Army situation.

The IRA engaged in attacks in their quest to have Northern Ireland secede from the rest of Britain.

Steyn said that with both the IRA and radical Islamic extremism, people who have been radicalized abroad and return home are likely guilty of treason.

"These guys traveled halfway down the planet to fight for the queen's enemies," he said.

Citing a German statistic of 60 monitoring agents for each terror suspect, Steyn said it would also be cost-effective to take suspects to court.

Watch the clip above.

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