Sen. Rand Paul on Tuesday introduced an amendment to the House-passed Foreign Intelligence Surveillance Act to protect Americans’ privacy, citing the case against former national security adviser Michael Flynn as an example of “abuse” and saying it “should never be allowed to happen again.”

Paul, R-Ky., who is an outspoken advocate for privacy reforms, proposed an amendment to the USA FREEDOM Reauthorization Act of 2020 – which passed the House on a bipartisan basis earlier this year – to protect Americans' privacy, ensure due process and “reassert the Fourth Amendment.”

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“It flies in the face of our Constitution that a secret court can authorize invading an innocent American’s privacy,” Paul said in a statement Tuesday. “Recent months have once again made all too clear how such a system leads to abuse. It’s time for Congress to stop paying lip service to reform and pass real safeguards that respect Americans’ rights.”

He added: “What happened to General Flynn and President Trump should never be allowed to happen again.”

Paul’s amendment would still allow the Foreign Intelligence Surveillance Court (FISC) to order surveillance of non-Americans and enemies abroad, but would require the government to obtain a warrant from a traditional federal court – as opposed to the secret FISC – to surveil an American.

The amendment would also prohibit the federal government from introducing into evidence any information gained from warrantless surveillance on an American, and would guarantee an American’s ability to use that evidence in their defense.

Paul’s proposal comes as the FISA bill hits the Senate floor and amid rapidly unfolding developments about the origins of the Russia investigation.

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Last week, the Justice Department dropped the case against Flynn, after they determined that the FBI’s 2017 Flynn interview – which formed the basis for his guilty plea of lying to investigators – was "conducted without any legitimate investigative basis.” His conversations with Russia's former ambassador to the U.S. were picked up during the presidential transition.

Meanwhile, FISA is at the center of the FBI’s original Russia probe. The FBI obtained FISA warrants to surveil former Trump campaign aide Carter Page.

DOJ Inspector General Michael Horowitz found widespread errors in the process of obtaining the warrant against Page, including that at least two FISA warrant renewals against Page lacked probable cause. Horowitz, in his report, also revealed that there were at least 17 “significant inaccuracies and omissions” in the Page FISA applications.

The FISA reform legislation requires more oversight to the process — including a requirement for the attorney general to personally sign off on surveilling government officials.

The bill will also expand when FISA judges should appoint an outsider to critique the government's position. Currently, judges are only to do so when addressing a novel and significant question of interpreting surveillance law.

The FISA reform bill includes stricter penalties for abusing the FISA process and the FISC for political purposes. False declarations before FISC or other FISA abuses, including engaging in electronic surveillance without authorization, disclosing or using information obtained by e-surveillance without authorization, will now have a penalty of up to eight years in prison, up from five.

The bill has a section stipulating the penalty also applies to “an employee, officer, or contractor of the United States Government [who] intentionally discloses an application, or classified information contained therein, for an order under any title of this Act to any person not entitled to receive classified information.”

Meanwhile, a controversial portion of the FBI’s surveillance powers, known as Section 215, gave the government broad powers to demand “business records” from companies in the name of national security investigations.

The new legislation allows obtaining business records to continue but bans using such an order to collect information like cell phone data that in a criminal investigation requires a warrant, which has a higher legal standard.

Fox News’ Chad Pergram, Morgan Phillips and Marisa Schultz contributed to this report.