Read: John Walker Lindh’s prison life isn’t so bad, but he’s still suing to pray

His more than 17 years in captivity seem, on the basis of this correspondence, to have converted Lindh from an al-Qaeda supporter to an Islamic State supporter.

According to reports, Lindh acquired an Irish passport a few years ago, and he intends to move to Ireland to proselytize once his probation ends in a few years. No one has said where he intends to live in the meantime, but one possibility is a return to Marin County, California, where he grew up in the 1990s and where his father still lives.

In 2002, George H.W. Bush, expressing his total lack of sympathy with Lindh, called him a “Marin County hot-tubber.”* (He later apologized for maligning Marin County when he had intended to malign only Lindh.) That nickname got to the heart of what irritates so many Americans about Lindh. He had everything: loving parents, wealth, a childhood in a fantasyland of pleasure and natural beauty. Before even reaching adulthood, he had rejected it all. He posed online as an aggrieved black man. After his conversion to Islam, he rejected every opportunity to live like most Muslims he met, and instead sought ever more extreme peers, first in the madrasas of Yemen, then in Pakistan, and finally in the al-Qaeda camps of Afghanistan.

As a member of al-Qaeda, he fought against the Northern Alliance, the local U.S. ally seeking to unseat the Taliban. Two American CIA operatives, Mike Spann and David Tyson, found and interrogated him at a fort in northern Afghanistan. Lindh’s fellow prisoners were hiding grenades, but Lindh said nothing during the interrogation, and in the minutes that followed, the prisoners overwhelmed and killed Spann.

The journalist Robert Young Pelton found Lindh the next day, wounded by shrapnel and hypothermic after the prison-uprising battle. “When I first met him, the thing that surprised me the most was that he didn’t want to talk to his parents,” Pelton says. He wanted martyrdom, and he said so. “Lindh seemed like a sociopath who had been working really hard to be with a group that was killing Americans and fellow Muslims.”

He was, Pelton says, an “obsessive.” And unfortunately, it appears that his obsessions have not varied. T. S. Ellis III, the federal judge who approved his probation, imposed strict rules on him, including a total ban on use of the internet and no contact with known extremists, presumably including his “colleague” Jibril. Authorities certainly know about Lindh’s continuing radicalism—not least because they have read every word of my correspondence with him.

The chances that he will leave prison and immediately start gathering bomb-making materials seem exceedingly slim to me. But the chances that Marin County will someday have an unrepentant jihadist praying in its mosques, and soaking in its (woman-free) hot tubs, seem very high. (ABC’s James Gordon Meek has reported that Lindh will initially live in Virginia, where he was sentenced.) Senators Richard Shelby and Maggie Hassan wrote to the Bureau of Prisons to ask why Lindh is out early. Their letter’s last points, though, cut to the deeper problem. What “policy, strategy, and process” do we have to ensure that a terrorist can “reintegrate into society”?