LONDON — American news outlets including The Chicago Tribune, The Los Angeles Times and The Arizona Daily Star abruptly blocked access to their websites from Europe on Friday, choosing to black out readers rather than comply with a strict new data privacy law in the European Union that limits what information can be collected about people online.

The new rules, known as the General Data Protection Regulation, strike at a core element of businesses that offer free content online but that make money by collecting and sharing user data to sell targeted advertising. The shutdowns came as a surprise to readers of the publications, because companies had two years to prepare for the new regulations.

The most notable blackouts were by news organizations tied to the American media company Tronc. In addition to The Chicago Tribune and Los Angeles Times, newspapers including The New York Daily News, The Orlando Sentinel and The Baltimore Sun were also unavailable to readers in Europe. (Tronc announced in February that it was selling The Los Angeles Times.)

“We are engaged on the issue and committed to looking at options that support our full range of digital offerings to the E.U. market,” the Tronc-owned newspapers said on their websites. “We continue to identify technical compliance solutions that will provide all readers with our award-winning journalism.”