Tougher State Department rules governing federal workers' speech -- covering everything from their congressional testimony to tweets -- have critics warning of a chilling effect that could be a way to put officials on notice as Congress probes the Benghazi attack and Hillary Clinton email scandal. 

“Boy, does this smell like bad fish,” said Peter Van Buren, an ex-foreign service officer who was squeezed out of his job in 2012 after he published a book and a personal blog critical of the State Department’s Iraq reconstruction efforts.  

“This does seem kind of coincidental that these new rules, after three years, have been issued in the same time frame as the Hillary Clinton [email] situation ... and looking forward to [Benghazi] hearings in October,” he told FoxNews.com. “It looks like they are trying to chill the speech of their employees.”  

The 19-page revised rules, first reported by the blog Diplopundit, were issued on July 27 and include three major changes or clarifications, critics say, that could clamp down on government workers’ speech. They include specific wording about congressional testimony, wait times for review of blog posts and social media like tweets, and additional restrictions on what material can be published in a personal capacity by either current or former employees.  

“It’s an absolute overreach,” Rep. Jason Chaffetz, R-Utah, chairman of the House Oversight and Government Reform Committee, told The Heritage Foundation's Daily Signal.

Sen. Chuck Grassley, R-Iowa, chairman of the Senate Judiciary Committee, also expressed concern, saying in a statement: "Any attempt by an agency to interfere with the testimony of former employees, who often feel free to be more candid about problems in their former agency, would weaken the checks and balances established by our Constitution."  

But the State Department maintained the changes are meant to help, not hinder, employees speaking publicly. State Department spokesman Mark Toner said the revisions “are more protective of employee speech as they establish a higher bar for limiting employees’ writing or speaking in their personal capacity, while also recognizing changing technologies in communication, such as social media.”  

He said the revisions streamline the review process and remind employees about existing rules regarding the disclosure of classified and other protected information.  

“The revisions do not change any procedures with regard to employee testimony before the courts or Congress,” Toner added.  

Still, the guidelines spell out that testimony from current or former employees must go through a review process, whether they are speaking in an official capacity or as a private citizen. While every agency requires some kind of pre-clearance before its employees speak on matters of official concern, the State Department “already has the tightest rules ever,” in terms of free speech, Van Buren said.  

“[These revisions] are important in what they do to employees, particularly potential whistleblowers, before they have spoken,” Van Buren said. “The real key here is anyone who is sitting here waiting out a decision to blow the whistle is going to see this and say, I don’t have a freaking chance.”  

He said the revisions are complicated but pointed to three areas of concern. First, they define in much greater detail who is covered; not only does it identify a wide range of current and former employees subject to review, but it says specifically that “employee testimony, whether in an official capacity or in a personal capacity on a matter of Departmental concern, may be subject to the review requirements.” 

"In practical terms," Diplopundit wrote, "we think this means that if you get summoned to appear before the House Select Benghazi Committee and [are] testifying in your personal capacity as a former or retired employee of the State Department, these new regulations may still apply to you, and you may still need clearance before your testimony."

Next, it lays out review time frames for blog posts and social media like tweets as five days and two days, respectively. That means employees and former employees must submit blog posts and tweets of official concern for review, and if they get no response in those time frames they can publish. Those submitting speeches and books must wait five and 30 days, respectively.

“I think it’s an understatement to say that that a two-day-old tweet tends not to be useful,” said Van Buren. 

Lastly, he said while individuals are free to publish after the allotted time expires if they get no response from State, the agency has put new restraints on content, meaning the author can be punished after the fact for publishing unacceptable content. The old rules said anything was game outside of classified material, personally identifiable information like Social Security numbers, contractual information and anything that might impede a law enforcement investigation. The new rules add, “Material that meets one or more of the criteria for exemption from public disclosure under the Freedom of Information Act (FOIA), 5 U.S.C. 552(b), including internal pre-decisional deliberative material.”  

Translation: Anything that might be redacted in documents released under FOIA could be a red flag -- and critics say this could be as simple as a conversation between two officials. “State can make a case about anything and everything,” Diplopundit wrote. 

In Van Buren's case, the agency tried to say he violated the classified material rule in his book, “We Meant Well: How I Helped Lose the Battle for the Hearts and Minds of the Iraqi People,” but the case fell apart. He was pushed into retirement anyway. “When people see rules like this, they realize the deck is stacked against them -- they will self-censor," he said. 

FoxNews.com's Kelley Vlahos and Fox News’ Lucas Tomlinson contributed to this report.