For months, the U.S. Justice Department vigorously opposed the unsealing of former president Richard Nixon’s 1975 testimony in the Watergate investigation, saying that disclosure would undermine the secrecy of grand jury proceedings.

DOJ lawyers argued judges don’t have the authority to craft exceptions to the federal ­criminal procedure rule that governs grand juries. The rule, as it stands, doesn’t recognize “historical significance” as a reason allowing a trial judge to override the confidentiality of grand jury proceedings.