Congressional Republicans have a plan to prevent deadly attacks like the Orlando nightclub massacre from happening again: Give the FBI easy access to citizens' browsing history and email data without the hassle of having to obtain a warrant first.

Arizona Senator John McCain filed an amendment to the Commerce, Justice, Science Appropriations Act on Monday night that would do exactly that, on the same day that many lawmakers voted against measures which would keep AR-15s out of the hands of potentially dangerous Americans.

"In the wake of the tragic massacre in Orlando, it is important our law enforcement have the tools they need to conduct counterterrorism investigations and track 'lone wolves'" McCain wrote in a statement.

So far, authorities investigating Orlando gunman Omar Mateen have concluded that he was a "lone wolf" actor who self-radicalized from consuming extremist propaganda online.

As a provision of the Patriot Act, which was passed after 9/11, the FBI can, without a warrant, force banks, phone companies, internet businesses, and others to hand over a customer's name, address, and billing records. But it needs a warrant to access citizens' email metadata, like details about who sent or received an email and when they sent it. The FBI also cannot access a citizen's web browsing history information without a warrant.

McCain's amendment would allow the FBI access to people's browsing histories and email metadata by broadening the scope of administrative subpoenas known as National Security Letters (NSL).

To put it simply, if the FBI wants to know what time you logged out of your Facebook account, they just need to submit an NSL to Facebook and demand they hand over that information. Often, companies like Google or Facebook will be under a gag order. They could be sharing information about your (not-so-private) online activities with federal agents, and you would be none the wiser.

McCain's amendment would also make permanent a section of the Intelligence Reform and Terrorism Prevention Act of 2004, also known as "the lone wolf provision."

Neema Singh Guliani, legislative counsel for the American Civil LIberties Union, co-wrote a letter to US senators urging them to oppose the amendment on Wednesday, when it is scheduled for a vote. But, she told VICE News, it's difficult to predict which way the Senate will vote.

"It's hard to know post-Orlando," Guliani said. "The dynamics can be different, people can be reactive, and there's often a push to get things through without proper debate or consideration... or recognizing the dangers and how concerning it is."

"[McCain's amendment] isn't a solution," Guliani added. "It's the opposite. It increases dangers for American liberties."

"This would strip out all the protections and buffers between [the government] and everyday citizens. It would allow the FBI to get this information with just a subpoena, under a shroud of secrecy. You may never know. These subpoenas are often accompanied by gag orders," Guliani said. "Abuses stay hidden."

In the letter, the ACLU says their concerns for the proposed amendment are "compounded by the government's history of abusing the NSL statute."

"In the past ten years, the FBI has issued over 300,000 NSLs, a vast majority of which included gag orders that prevented companies from disclosing that they received a request for information," the letter states. "An audit by the Office of the Inspector General (IG) at the Department of Justice in 2007 found that the FBI illegally used NSLs to collect information that was not permitted by the NSL statutes."

Lawmakers previously attempted to pass the provision by sneaking it into a secretive Senate intelligence bill last month.

Earlier this year, FBI director James Comey made it clear that getting the spy bill passed was a priority for the agency, and was criticized for presenting it as a mere "typo," downplaying the ramifications it would really have on American privacy.

"We do know that where the FBI is concerned, they generally don't stop pushing for what they want until they get it," Robyn Greene, policy counsel at the Open Technology Institute, wrote in February. "Even if it takes decades, they tend to wait for an opportune moment to push their agenda over the finish line or they simply wear Congress down until it gives them what they want."

Other Republicans who blessed McCain's insertion of the provision into the Commerce bill today included North Carolina Senator Richard Burr, Texas Senator John Cornyn, Alabama Senator Jeff Sessions and Senate Majority Leader Mitch McConnell.