A U.S. District Judge in Oregon has blocked a $25 billion-bid by supermarket giant Kroger to take over rival Albertsons after ruling that the Federal Trade Commission's concerns about the merger's impact on market consolidation were valid.

In an historic ruling for labor and antitrust advocates, a federal judge blocked the $25 billion merger of grocery giants Kroger and Albertsons.

Judges in Oregon and Washington on Tuesday blocked supermarket giants Kroger and Albertsons from merging, throwing into question the future of the largest proposed grocery merger in U.S. history. U.S.