The 9-0 decision reflected the justices' view Andersen's conviction in a document-shredding case was faulty because "jury instructions at issue simply failed to convey the requisite consciousness of wrongdoing."
Not only was the decision unanimous, it was quick: Oral arguments were heard less than a month ago.
The ruling throws the case back to lower federal courts, which may throw out the case altogether or grant Andersen a new trial, CNN reported.
"We pursued an appeal of this case ... because we had an obligation to set the record straight and clear the good name of the 28,000 innocent people who lost their jobs at the time of the indictment and tens of thousands of Andersen alumni," the firm said Tuesday.
Andersen executives were convicted in 2002 of obstruction of justice over the massive document destruction relating to its work for Enron, the energy services giant that a year before was facing a government probe of its complex finances.