They lied. Is anyone shocked?

A much-awaited final report by the United Nations' nuclear inspection agency on Iran's past nuclear activities has concluded that Iran worked on a nuclear weapons program until 2009 - although Tehran still insists its nuclear-energy program is peaceful.

The good news: The nuclear sleuths of the International Atomic Energy Agency, led by their intrepid director, Yukio Amano, managed to ferret out crucial information despite the obstructions of Iranian officials. And the IAEA was bold enough to make its skepticism public, despite expectations it might soften its report so as not to jeopardize the nuclear accord that Tehran reached in July.

Yet critics of the deal will ask the obvious question: If Iran won't come clean about its past, can it be trusted in the future? The obvious answer: Don't trust but verify, verify, verify.

According to the terms of the nuclear accord, the IAEA's report on Iran's past activities - even though damning - won't stop the lifting of economic sanctions, so long as Tehran keeps its pledge to sharply limit its nuclear-fuel production and dismantles much of its nuclear infrastructure.

"A number of observers will be disturbed that Iran appears to be getting away with the big lie, benefiting from sanctions relief while stonewalling the investigation," wrote Robert Einhorn, a former State Department official involved in the nuclear negotiations, in the National Interest.

But, as Einhorn told me in a phone interview, the West already had good information on Iran's past activities. The critical need is to focus on future verification. "It is important for the United States to signal it will impose compliance and that violations would mean that sanctions could come back," he said.

The report does demonstrate that, with new technologies available, Iran won't have an easy time cheating in the future. For a decade Tehran's leaders have stonewalled IAEA inspectors, refusing to answer questions about a suspected secret program to design a warhead that could fit atop a nuclear missile.

As part of the nuclear accord, Iran was required to respond to a series of questions about those activities before sanctions could be lifted, especially what went on at the Parchin military complex. Until September, the IAEA was only able to monitor activities using satellite imagery.

But by comparing previous satellite images with what they saw at Parchin, the IAEA was able to conclude that a large cylindrical-shaped object that was installed in 2000 and looked like an explosives firing chamber was no longer present. Inspectors noted that the area where the object had appeared had been recently renovated by the Iranians. And from the environmental samples it took, the IAEA was able to debunk the Iranian claim that the Parchin site was merely storing chemicals for civilian use. The inspectors also identified particles that appeared to indicate nuclear material had been used at the site.

"What the report indicates," says Einhorn, "is that even without Iranian cooperation the inspectors were still able to reach damning conclusions."

However, skeptics fear that once sanctions are lifted, and Western firms establish new economic ties with Iran, the Europeans will be reluctant to recognize violations or to impose new sanctions. Moreover, the provisions for sanctions "snapback" are complex. And, Iran's supreme leader, Ayatollah Ali Khamenei, has indicated (contrary to the terms of the deal) that any restoration of sanctions for any reason would end Iranian compliance with the accord.

This raises serious questions on whether President Obama will be willing to jeopardize his signature foreign-policy achievement by pressing Tehran too hard.

To counter any such Iranian misconceptions, says Einhorn, "it is important for the United States to signal it will impose compliance and that violations would mean sanctions could come back. We must make clear there is a strong U.S. commitment to prevent Iran from developing a nuclear weapon and that the U.S. is prepared to use military force to stop them."

Moreover, he says, it is fully within U.S. rights to impose specific sanctions on Iran for egregious behavior in the Mideast, such as aiding terrorist groups, including Hezbollah. Such sanctions were not excluded by the nuclear agreement. "We need to show Iran we are not so protective of this deal that we won't implement our own rights for fear of jeopardizing it," says Einhorn.

That doesn't mean congressional critics should try to kill the deal by reimposing economic sanctions whose lifting was part of the accord. But it does mean using all intelligence means (in close cooperation with Europe and Israel) to watch for Iranian cheating.

And the White House must make clear it won't give Iran a pass on new cheating (which critics claim is already occurring). The IAEA has shown Iran will have a hard time conducting secret operations. Obama needs to convince the Iranians that, if they try, they will pay a high price.