When Twitter decided briefly last fall to block users from posting links to an article about Joseph R. Biden Jr.’s son Hunter, it prompted a conservative outcry that Big Tech was improperly aiding Mr. Biden’s presidential campaign.

“So terrible,” President Donald J. Trump said of the move to limit the visibility of a New York Post article. Senator Josh Hawley, Republican of Missouri, said Twitter and Facebook were censoring “core political speech.” The Republican National Committee filed a formal complaint with the Federal Election Commission accusing Twitter of “using its corporate resources” to benefit the Biden campaign.

Now the commission, which oversees election laws, has dismissed those allegations, according to a document obtained by The New York Times, ruling in Twitter’s favor in a decision that is likely to set a precedent for future cases involving social media sites and federal campaigns.

The election commission determined that Twitter’s actions regarding the Hunter Biden article had been undertaken for a valid commercial reason, not a political purpose, and were thus allowable.

And in a second case involving a social media platform, the commission used the same reasoning to side with Snapchat and reject a complaint from the Trump campaign. The campaign had argued that the company provided an improper gift to Mr. Biden by rejecting Mr. Trump from its Discover platform in the summer of 2020, according to another commission document.

The election commission’s twin rulings, which were made last month behind closed doors and are set to become public soon, protect the flexibility of social media and tech giants like Twitter, Facebook, Google and Snapchat to control what is shared on their platforms regarding federal elections.

Republicans have increasingly been at odds with the nation’s biggest technology and social media companies, accusing them of giving Democrats an undue advantage on their platforms. Mr. Trump, who was ousted from Twitter and Facebook early this year, has been among the loudest critics of the two companies and even announced a lawsuit against them and Google.

The suppression of the article about Hunter Biden — at the height of the presidential race last year — was a particular flashpoint for Republicans and Big Tech. But there were other episodes, including Snapchat’s decision to stop featuring Mr. Trump on one of its platforms.

The Federal Election Commission said in both cases that the companies had acted in their own commercial interests, according to the “factual and legal analysis” provided to the parties involved. The commission also said that Twitter had followed existing policies related to hacked materials.

The rulings appear to provide social media companies additional protections for making decisions on moderating content related to elections — as long as such choices are in service of a company’s commercial interests. Federal election law is decades old and is broadly outdated, so decisions by the election commission serve as influential guideposts.

Campaign finance law “does not account for the post-broadcast world” and puts few restrictions on the behavior of social media firms, said Ciara Torres-Spelliscy, a law professor at Stetson University. “There is a real mismatch between our federal campaign finance laws and how campaigns are run.”

Still, the Republican National Committee’s complaint stretched the boundaries of campaign finance law, she added. “The choice to delete or suppress certain content on the platform is ultimately going to be viewed through the lens of the First Amendment,” Ms. Torres-Spelliscy said. “I don’t think that type of content moderation by the big platforms is going to raise a campaign finance issue.”

Some Republicans are seeking to take a broader cudgel to the big internet companies, aiming to repeal a provision of communications law that shields them from liability for what users post.

In the case of the Hunter Biden article, Twitter reversed course within a day of its decision to block distribution of the piece, and its chief executive, Jack Dorsey, has called the initial move a “mistake.”

The Federal Election Commission’s official vote on the case — the commission is split equally between three Democratic-aligned commissioners and three Republicans — is not yet public, nor are any additional statements written by commissioners. Such statements often accompany the closure of cases and can provide further insight into the commission’s reasoning.

In addition to rejecting the R.N.C. complaint, the commission dismissed other allegations that Twitter had violated election laws by “shadow banning” Republican users (or appearing to limit the visibility of their posts without providing an explanation); suppressing other anti-Biden content; and labeling Mr. Trump’s tweets with warnings about their accuracy. The commission rejected those accusations, writing that they were “vague, speculative and unsupported by the available information.”

Twitter and Snapchat declined to comment.

Emma Vaughn, an R.N.C. spokeswoman, said the committee was “weighing its options for appealing this disappointing decision from the F.E.C.” A representative for Mr. Trump did not immediately respond to a request for comment.

Twitter would go on to permanently bar Mr. Trump from its platform entirely in January, citing “the risk of further incitement of violence” after the attack on the Capitol by his supporters as Congress voted to certify the 2020 election.

Out of office, Mr. Trump has sued Facebook, Twitter and Google, arguing that a provision of the Communications Decency Act known as Section 230, which limits internet companies’ liability for what is posted on their networks, is unconstitutional.

Legal experts have given little credence to Mr. Trump’s suit, the news of which the former president immediately used as a fund-raising tactic.

Section 230 has been a regular target of lawmakers who want to crack down on Silicon Valley companies. While in office, Mr. Trump signed an executive order intended to chip away at the protections offered by Section 230, and Democratic and Republican lawmakers have proposed repealing or modifying the provision.

But technology companies and free speech advocates have vocally defended it, arguing that Section 230 has been crucial for the growth of the internet. If the measure were repealed, it would stifle free speech and bury social media companies in legal bills, the companies have said.

Twitter initially said that it had prevented linking to the Hunter Biden article because of its existing policies against distributing hacked materials and private information. The article, which focused on the Bidens’ Ukrainian ties, involved correspondence that The Post suggested had been found on Hunter Biden’s laptop.

But Mr. Dorsey, Twitter’s chief executive, acknowledged in October that blocking links “with zero context as to why” had been “unacceptable.”

Soon after, Twitter said that it was changing its policy on hacked materials and would allow similar content to be posted, including a label to provide context about the source of the information.

Republicans said the damage was done — and set a poor precedent.

“This censorship manifestly will influence the presidential election,” Senator Hawley wrote in a letter to the F.E.C. last year after Twitter blocked the article and Facebook said it was “reducing its distribution” of the piece.

The commission documents reveal one reason that Twitter had been especially suspicious of the Hunter Biden article. The company’s head of site integrity, according to the commission, said Twitter had “received official warnings throughout 2020 from federal law enforcement that ‘malign state actors’ might hack and release materials associated with political campaigns and that Hunter Biden might be a target of one such operation.”

The election commission said it found “no information that Twitter coordinated” its decisions with the Biden campaign. In a sworn declaration, Twitter’s head of U.S. public policy said she was unaware of any contacts with the Biden team before the company made its decisions, according to the commission document.

Adav Noti, a senior director at the Campaign Legal Center, said that he supported the rulings but that he had concerns about the election commission’s use of what he called the “the commercial rationale,” because it was overbroad.

“It encompasses almost everything for-profit corporations do,” Mr. Noti said.