An influential federal judge shut down a high-profile patent case involving Apple Inc. and Google Inc.'s Motorola Mobility unit, rejecting their use of a legal weapon at the heart of the current smartphone patent wars.

The ruling Friday by Richard Posner, an appellate-court judge designated to hear the case in Chicago, is a blow to the campaign by Apple and its rivals to use patent suits to block competitors' progress. Judge Posner ruled that companies in such cases shouldn't be able to win court injunctions blocking sales of infringing products, a key tactic for plaintiffs trying to pressure defendants.

Read more at The Wall Street Journal