In "Unimatrix Zero", Janeway and Tuvok's command codes are still active, even though they're on a dangerous mission in the Borg Queen's Command Cube. Wouldn't it be SOP for the security of starships to lock out command codes under similar situations? Chakotay even remarks after Borg weapons are cutting though Voyager's hull: "They must have gotten Tuvok's command codes."
Was this malfeasance on the part of Chakotay?