US Bancorp and Wells Fargo & Co. lost a foreclosure case in Massachusetts' highest court that will guide lower courts in that state and may influence others in the clash between bank practices and state real estate law. The ruling drove down bank stocks.

The state Supreme Judicial Court today upheld a judge's decision saying two foreclosures were invalid because the banks didn't prove they owned the mortgages, which he said were improperly transferred into two mortgage-backed trusts.