Righthaven, the firm MediaNews Group uses to sue bloggers and websites for posting newspaper content without permission, suffered a serious setback today in federal court in Las Vegas, according to the Las Vegas Sun and Wired.com.

Chief U.S. District Judge Roger Hunt ruled that Righthaven misled the court and doesn’t have standing to sue on behalf of newspapers who claim their copyrights were infringed. Hunt threatened to impose sanctions against Righthaven.

Here’s how Righthaven enforces copyrights. When a publisher feels its copyright has been infringed, usually by somebody on the internet, it sells the copyright of the story or photograph to Righthaven. Righthaven then sues the alleged infringer, seeking damages. Righthaven has filed 274 copyright lawsuits since March 2010.

In order to file lawsuits, copyright plaintiffs have to have actual control of the copyrights, not just the right to sue, Hunt found.

MediaNews Group’s Denver Post and the Las Vegas Sun Review-Journal, owned by Stephens Media Group (a minority partner in MNG’s Bay Area newspapers), used Righthaven to go after alleged copyright infringers. Today’s ruling comes in a case against the political website Democratic Underground, which posted just four paragraphs of a 34-paragraph Las Vegas Review-Journal story about then-U.S. Senate candidate Sharron Angle. Democratic Underground credited the Review-Journal and provided a link to the paper’s website containing the story. By providing credit and a link, the website argued that its use of the four paragraphs constituted “fair use” under the copyright law.

The Las Vegas Sun, in its news story about the ruling, said Hunt’s ruling “could shut down Righthaven’s lawsuit campaign.”

<b>Correction: In the penultimate graf of the item above, the newspaper owned by Stephens Media was incorrectly identified as the Sun. It’s actually the Review-Journal.</b>