European regulators' decision to bring antitrust charges against Amazon.com Inc. could be a harbinger of developments in the U.S., with regulatory uncertainty likely to extend well into 2021, legal and industry experts say.

In charges announced Nov. 10, the European Commission accused Amazon of violating EU antitrust rules by using data from third-party sellers on its platform to compete against them with its own retail business. The majority of sales on Amazon's site are sold by third-party merchants.

Amazon faces similar allegations in the U.S., where lawmakers have alleged that the company is undercutting small businesses by using data from third-party sellers to inform its own products.

"We disagree with the preliminary assertions of the European Commission and will continue to make every effort to ensure it has an accurate understanding of the facts," an Amazon spokesperson said in an email to S&P Global Market Intelligence. "Amazon represents less than 1% of the global retail market, and there are larger retailers in every country in which we operate."

The European charges are the latest effort by regulators there to restrain the market power of U.S. tech companies. EU regulators are also looking to enforce a new set of rules that would require online platforms to verify the identities of sellers before their services can be used.

Industry experts say the charges come as no surprise given that Europe has taken a lead role in tackling competition issues related to Big Tech, and similar actions could be brought in the U.S.

"Given the ongoing state and federal investigations into Big Tech, U.S. enforcers could well raise issues similar to the EU in a case against Amazon," Diana Moss, president of the American Antitrust Institute in Washington D.C., said in a Nov. 10 email.

While it is unclear whether U.S. regulators would wait to see what happens in Europe before considering their own case, the competitive issues raised in Europe are a "long-standing monopolization concern," and similar concerns could form the basis of a U.S.-based antitrust case against Amazon, Moss said.

Alex Petros, policy counsel at the Washington, D.C.-based nonprofit public interest group Public Knowledge, noted that there has been strong bipartisan support for more stringent antitrust regulations throughout 2020, and that is likely to continue under an administration led by U.S. President-elect Joe Biden.

Petros said the Biden administration will likely pursue the U.S. Justice Department's current lawsuit against Alphabet Inc.'s Google unit, which alleges that the company illegally maintained monopolies in general search, search advertising, and general search text advertising markets. The Federal Trade Commission has also been examining Amazon's relationship with third-party sellers.

"I would not be surprised to see something from the FTC or the DOJ along these same lines," Petros said in an interview. "I think you are going to see some bills out of the House, I think you are going to see some bills out of the Senate. You'll see some serious movement in this area in 2021."

Amazon shares ended the day down 3.46% at $3,035 while the Nasdaq lost 1.37%.

Harbinger of things to come

The charges add to a series of efforts in the U.S. and abroad to address competition issues around Big Tech that is unlikely to slow in the coming year, industry analysts say.

"I think this is a continued theme where the E.U. is more and more focused against Big Tech players with Amazon front and center, so it's not a shock to the Street that they continue to ratchet up the monopoly talk," said Daniel Ives, an analyst with Wedbush Securities, in an interview. "Ultimately it's a harbinger of things to come when you look at what Amazon as well as every Big Tech company is facing not just in the E.U. but in the U.S."

Mark Shmulik, an analyst with AB Bernstein, said the European Commission's charges could result in substantial fines of as much as $4 billion or $5 billion and "guardrails" around where and when third-party data can be used. But he also cautioned that it will be very difficult to prove that Amazon is engaging in antitrust activity. "The bar is so high," he said.