WASHINGTON—A federal judge ruled Congress can get its hands on grand-jury evidence collected by former special counsel Robert Mueller, and also determined that wide-ranging House inquiries into President Trump have legal standing as an impeachment investigation.

U.S. District Judge Beryl A. Howell granted a request from the House Judiciary Committee for access to material that was redacted from the 448-page special counsel report, released in the spring, as well as some of the exhibits and transcripts referenced in the report....