Homeland Security Secretary Janet Napolitano has taken much of the criticism about the U.S. government's failure to stop the underwear bomber bound for Detroit.

But the vitriol is misplaced. None of the responsibility for keeping the attempted killer off the plane rests with the Department of Homeland Security (DHS). On the contrary, the many obstacles Congress and both the Bush and Obama administrations have thrown in front of the department kept it from playing a more proactive role in safeguarding the homeland.

Ms. Napolitano walked into harm's way when she toured the Sunday talk shows as the "face" of the administration's response. Her statement that "the system worked" proved to be the media equivalent of having a "kick me" sign taped to her back. What Ms. Napolitano was actually referring to was the department's system for alerting international flights worldwide in the wake of a threat. That system did work like a charm. Unfortunately, it seemed she was referring to the aviation security system designed to keep would-be bombers off planes to begin with.

Beyond media gaffes, when the dots started to get connected it was pretty clear that Umar Farouk Abdulmutallab should have been stopped before he bought his ticket, let alone before he boarded a plane. None of the layers of security between him and us, however, were controlled by the Department of Homeland Security.

That starts with the screening before boarding. There was adequate security at Amsterdam to find the bomb. A simple pat-down in secondary screening would have done it. That screening, however, is done by the Dutch - not the Transportation Security Administration (TSA), an agency under the Homeland Security Department.

The decision to flag an individual for secondary screening or bar him from flying altogether comes from the Terrorist Watch and No-Fly lists. These lists are not controlled or managed by DHS. By law, Congress insisted the airlines - not TSA - do the screening. And airlines only have access to the No-Fly list. Mr. Abdulmutallab's name was not on the list.

Lists are managed by the National Counterterrorism Center and the Terrorist Screening Center. By law, Congress directed that the centers be run by the director of National intelligence and the FBI, respectively. Homeland Security is just another customer. The department has little ability to drive the policy, protocol or operations of the centers.

Next, Mr. Abdulmutallab shouldn't have been given a visa or, if he already had one, it should have been revoked. Yet Homeland Security has almost no authority to address this problem.

Visas are issued by the State Department. Under law, the Department of Homeland Security is supposed to set security policies for the State Department consular affairs offices that issue visas. That has never happened because of squabbling between the two departments. Likewise, embassies have been reluctant to accept visa security officers from Homeland Security who could work with the consular officers in identifying security gaps and threats. Neither Congress nor either administration has done anything about that.

Finally and most importantly, intelligence agencies and international cooperation with key allies (such as Britain) should have discovered and stopped the plot, as they did with the 2006 London-based liquid-bomb plot. That didn't happen this time.

From the start, Homeland Security has been treated like the weak sister of the intelligence and counterterrorism community. Washington hasn't done much to address that, either.

Picking on Homeland Security might make sense if the latest attempted attack was the department's fault - but it wasn't. Dumping billions more on aviation security might make sense if we could guarantee this won't happen again. We can't.

The best way to stop terrorist attacks is to block them before they start. That's a better answer than striking out at DHS or dumping more money into wasteful programs that try to "child-proof" America against every potential terrorist attack.

Congress could start taking the department seriously by consolidating oversight from many dozens of committees and subcommittees to something more streamlined (such as the oversight structure for the Defense Department). Or lawmakers could just keep shooting the messenger.

James Jay Carafano, Ph.D., is Assistant Director of the Kathryn and Shelby Cullom Davis Institute for International Studies and Senior Research Fellow for National Security and Homeland Security in the Douglas and Sarah Allison Center for Foreign Policy Studies at The Heritage Foundation.