How Facebook decides which stories go into its Trending topics is not the government's concern, but it wouldn't be wise for the company to ignore a congressional request for an explanation of its practices, top media lawyers told CNNMoney.

"If Facebook ignores this request they could receive a subpoena, so I suspect they will cooperate," said Stephen Strauss, a former journalist who is now an attorney at Bryan Cave specializing in First Amendment issues.

He was referring to a letter sent by Senator John Thune to Facebook CEO Mark Zuckerberg seeking an explanation of how Trending stories are selected and whether any conservative stories were taken out of the list or liberal leaning stories were inserted.

Joe Larsen of Sedgwick Law agrees that it would be risky for Facebook to ignore the request.

"That's just not a good idea, even where... I can see no clear legal basis for Senator Thune's request," Larsen said. "I expect Facebook will provide quite a bit of information."

Related: Did Facebook suppress conservative news?

One piece of what Thune is seeking was revealed Thursday when The Guardian published Facebook's manual for people who manage the Trending topics feature. Facebook confirmed the veracity of the 20 page document, which reveals that there is a lot of human decision making in choosing the stories on top of what the company's algorithms suggest. The manual includes when stories can be "injected" into the Trending topics list.

The controversy began on Monday when Gizmodo published a report with anonymous allegations that former contractors had ignored Facebook's algorithms for its Trending topics section and that links to conservative news stories were "routinely" suppressed.

Thune demanded to know exactly how Facebook decides what news stories to publish and to see a list of all the stories that were previously not distributed or manually inserted into Trending topics.

As a platform that's used by over 222 million people in the United States and Canada, the company is able to influence the perceptions of a large chunk of the U.S. population, Thune said.

Facebook has denied that anyone improperly tinkered with the list or that they were instructed to do so. A company spokesman said, "We have received Sen. Thune's request for more information about how Trending Topics works, and look forward to addressing his questions."

Related: Facebook's 'trending topics' spark debate

According to Strauss, Thune's request was legitimate.

"I think that this situation is different than an inquiry into a news organization's content," he said. "In this case Facebook has a 'trending' feature, and Facebook affirmatively stated particular standards for this 'trending' feature, and now there is some question as to the veracity of those representations."

Mark Bailen, a media attorney at BakerHostetler, disagrees. He argues that Facebook has the same right to distribute the news "without interference from the government" as any company or individual.

"It's well established that the government has no role in dictating what is newsworthy," said Bailen. "The idea that the government is going back and looking into and investigating [Facebook's activities in distributing the news] conflicts with decades of jurisprudence under the First Amendment."

Floyd Abrams, a prominent First Amendment attorney, compares Thune's request to one issued by Congress in the 1970s when politicians sought to require CBS to turn over outtakes of a controversial CBS documentary, "The Selling of the Pentagon." The network refused and eventually the inquiry was dropped.

"It was an example of a news organization that was prepared to take great risks to defend its editorial independence," said Abrams.

Related: Senate demands answers from Facebook

"I don't mean to suggest that Facebook must remain silent when it is under attack. But it should take care not to cede its own hard won authority about what articles to cite or recommend to Congress."

One issue about this controversy that troubles some is the way that Facebook depicts its role in selecting what news is shown.

"It has always represented itself as an unbiased aggregator of news on its trending site," according to Larsen. "That is, Facebook says it doesn't have an editorial position."

After the Gizmodo report was published, Facebook Trending manager Tom Stocky wrote that the company has "rigorous guidelines in place for the review team to ensure consistency and neutrality."

Those guidelines don't allow reviewers to suppress or prioritize political perspectives or media outlets, he says. And these are the guidelines that Thune and others want to know more about.

The company's official description of the feature is simply: "a list of topics and hashtags that have recently spiked in popularity on Facebook. This list is personalized based on a number of factors, including Pages you've liked, your location and what's trending across Facebook."

Until the Gizmodo report, many people weren't aware that Facebook had a team to oversee the Trending Topics feature.

Suzy Fulton, a technology lawyer said that it's possible someone might sue Facebook based on fraud or deceptive practices -- but it would be hard to see what the damages would be, "even assuming you have a valid claim to begin with."

"We are certainly a litigious society," she said. "[But] you can opt out, you can go to Fox or some other conservative news media for your news if you feel Facebook is not telling the right story on its Trending Topics."