This undated photo provided by the U.S. Marshal's office shows Adel Daoud, of Hillside, Ill. Daoud is charged with terrorism for allegedly trying to set off what he thought was a car bomb Sept. 14, 2012, near a downtown Chicago bar. (AP/AP)

Four days before a sweeping government surveillance law was set to expire last year, Sen. Dianne Feinstein, the chairman of the chamber’s Intelligence Committee, took to the Senate floor. She touted the law’s value by listing some of the terrorist attacks it had helped thwart, including “a plot to bomb a downtown Chicago bar” that fall.

“So I believe the FISA Amendments Act is important,” the California Democrat said before a vote to extend the 2008 law, “and these cases show the program has worked.”

Today, however, the government is refusing to say whether that law was used to develop evidence to charge Adel Daoud, a 19-year-old Chicago man accused of the bomb plot.

And Daoud’s lawyers said in a motion filed Friday that the reason is simple. The government, they said, wants to avoid a constitutional challenge to the law, which governs a National Security Agency surveillance program that has once again become the focus of national debate over its reach into Americans’ private communications.

“Whenever it is good for the government to brag about its success, it speaks loudly and publicly,” lawyers Thomas Durkin and Joshua Herman wrote in their motion. “When a criminal defendant’s constitutional rights are at stake, however, it quickly and unequivocally clams up under the guise of State Secrets.”

If the government acknowledged that it had used evidence derived from the FISA Amendments Act, Daoud would have standing to challenge the law’s constitutionality. Specifically, Daoud’s lawyers would be able to take on a provision known as Section 702. The law permits the interception of foreign targets’ ­e-mails and phone calls without an individual warrant, including when the foreigners are in communication with Americans or legal residents.

The U.S. Supreme Court in February rejected a constitutional challenge to Section 702 by a group of journalists, lawyers and human rights advocates, saying they had no standing to sue because they had not proved that their communications had been intercepted.

But the court also said that if the government intends to use information derived from the Section 702 surveillance in a prosecution “it must provide advance notice of its intent,” and a defendant may challenge the lawfulness of the surveillance. The government assured the court that it would give such notice to criminal defendants.

In a filing this month in Chicago, U.S. Attorney Gary S. Shapiro refused to say whether the evidence was obtained under Section 702. Instead, he said, the government told Daoud the evidence was acquired pursuant to a traditional FISA court order, rather than under the expanded surveillance program authorized in 2008. A traditional order requires the government to go to a FISA judge and show probable cause that the target is an agent of a foreign power.

Daoud’s attorneys say in their pleading that the government is being disingenuous. “We believe it is clear that the evidence . . . came from Section 702,” Durkin said in an interview. “Either Senator Feinstein’s information was correct in December 2012, or she was given wrong information. The government has never disputed what she said.”

A spokesman for the U.S. attorney’s office had no comment but noted that the office had replied to Daoud’s initial request for notice earlier this month in Shapiro’s filing.

“The most troubling part of the case is the government seems to be trying to hide the ball,” said Alex Abdo, a staff attorney for the American Civil Liberties Union, which argued the Supreme Court case on behalf of the journalists, lawyers and activists. “They told the Supreme Court not to worry about reviewing the FISA Amendments Act because it would get reviewed in a criminal case. They said if they used the evidence in a criminal case, they’d give notice. Now they’re telling criminal defendants they don’t have to tell them. It’s a game of three-card monte with the privacy rights of millions of Americans.”

Abdo said the original FISA statute, passed in 1978, requires the government to notify defendants when evidence being used against them is derived from surveillance authorized by the law. The court, he said, should require the government to abide by the law. “Otherwise,” he said, “the most sweeping surveillance program ever enacted by Congress will never be reviewed in public by a court.”

Similarly, Stephen I. Vladeck, a law professor at American University, said, “Everyone knows the role that Section 702 is playing in a case like this.” But, he said, “thanks in part to the Supreme Court, the government can use Section 702 and then never have to defend its constitutionality.”

The central problem with Section 702, critics say, is its breadth and lack of individual warrants. The law targets non-U.S. persons “reasonably believed” to be located outside the United States but does not require that the government obtain a warrant before intercepting communications.

Moreover, the purpose of the collection is “foreign intelligence,” a broad category that may include everything from information on terrorism to nuclear proliferation to what a European journalist is writing on human rights abuses or an African businessman is saying about global financial risk, experts say.

According to a criminal complaint filed by an FBI agent, Daoud received an e-mail in February 2012 regarding his registration with an online jihadi forum overseas. In May 2012, Daoud sent himself a link for nine issues of Inspire magazine, an online publication put out by al-Qaeda in the Arabian Peninsula, an al-Qaeda affiliate.

That same month, two FBI undercover employees posing as jihadists contacted Daoud online in response to material he had posted. Between July and September, an undercover FBI agent met Daoud in Chicago and helped him plan the attack.

Daoud was arrested in September after he attempted to detonate a bomb placed in a jeep outside a Chicago bar with a remote-triggering device.

Durkin said that he thought the FBI used surveillance powers under Section 702 to identify Daoud and then got a traditional FISA order to conduct its sting against him.

“Nonetheless,” he said in the motion Friday, “the government’s interest in confusing these two issues is obvious. If it can avoid giving proper notice to defendants, as it seeks to do here, the government can avoid a challenge to the [FISA Amendments Act] altogether.”

U.S. District Judge Sharon Johnson Coleman has set a trial date for February.