There´s no question that the rebels Americans are currently fighting for in Libya include in their ranks jihadis who in recent years traveled to Iraq and Afghanistan to kill Americans. The only question is whether that worries you or not.

Take Abdel-Hakim al-Hasidi, a leader of U.S.-supported rebels in the fighting for Adjabiya. His hometown, Darnah, has produced many jihadis, and after the Sept. 11 attacks al-Hasidi traveled to Afghanistan to fight the "foreign invasion" -- that is, the U.S. military. According to a report in Britain´s Daily Telegraph, al- Hasidi says he was later captured in Pakistan, handed over to the U.S., then held in prison in Libya before being released in 2008.

In addition to fighting the U.S. in Afghanistan, al-Hasidi also says he recruited about two dozen men to fight the U.S. in Iraq.

Now al-Hasidi and his allies are moving toward Tripoli, which would not be possible without the military power of the United States. The men who devoted so much energy to killing Americans are now thankfully watching Americans kill for them.

To some observers, that´s no big deal. "No one seems all that frightened by him," the New York Times wrote of al-Hasidi after a visit to Darnah in early March. Al-Hasidi, the paper reported, "praises Osama bin Laden´s ´good points´ but denounces the 9/11 attacks on the United States." And besides, the Times reported, al-Hasidi finds it amusing that the government of Moammar Gadhafi considers him an al Qaeda terrorist. "He promised to lay down his arms once victory is won and return, he said, to teaching," the Times reported.

Maybe you believe that. Maybe you don´t. The problem is, al-Hasidi is by no means alone. We know that from intelligence gained in the Iraq War.

During that war, American strategists became increasingly concerned by the number of foreign fighters who came to Iraq to take up arms against the U.S. In an October 2007 raid near Sinjar, Iraq, American forces captured a computer that had biographical information on about 700 foreign terrorists who had come to Iraq between August 2006 and August 2007. An analysis of the so-called "Sinjar documents" found that Libya sent more fighters to the Iraqi front than any other country except Saudi Arabia; Libyans accounted for nearly 20 percent of the foreign fighters in the Sinjar documents.

Some of those Libyans were from an al Qaeda-affiliated organization called the Libyan Islamic Fighting Group, whose membership reportedly included one Abdel-Hakim al-Hasidi. In 2004, then-CIA Director George Tenet named the Libyan Islamic Fighting Group part of the "next wave" of terrorism that could threaten U.S. security whether or not al Qaeda was destroyed.

So what should the United States do about Libyan fighters who went to Iraq to kill Americans? And Libyans who went to Afghanistan to kill Americans? And Libyans who recruited them and helped them with their travels? Should we be hunting those people down? Or should we be fighting on their behalf?

"It´s a real concern, there´s no ifs, ands or buts about it," says Michael Rubin, a Middle East scholar at the conservative American Enterprise Institute. "The question for policymakers is, does that concern mean we should not be seeking change in those countries?" Rubin supports U.S. involvement in the Libyan war and believes the number of people like al-Hasidi is relatively small. "It´s not a reason not to support the rebels," he says. "It is a reason not to arm them, or not to trust others to arm them."

As for the jihadis who killed Americans in Iraq and Afghanistan, Rubin would like to see U.S. "hit teams" take care of them. But that, of course, would be way, way, way outside the United Nations Security Council Resolution that guides American actions in Libya. If the U.S.- led coalition prevails, it seems likely that some of the jihadis will choose not to return to lives as humble schoolteachers, as al-Hasidi claims, but instead become part of the new leadership of Libya.

There´s no way the U.S. can be involved in an action like the Libyan war without coming in contact with some pretty bad actors. That´s a good reason not to be involved in an action like the Libyan war. But even if involvement is an ugly necessity, do we have to give active support and protection to people who have devoted their lives to killing Americans?