His subpoena would not meet the Supreme Court's standard for enforceability, as outlined in their decision in "The United States vs. Nixon:" (It is) "Congress’ duty to articulate its
need for particular materials — to “point] to ... specific legislative decisions that cannot responsibly be made without access to materials uniquely contained in the privileged document it has requested. Moreover, this case suggests that Congress will seldom have any legitimate legislative
interest in knowing the precise pre-decisional positions and statements of particular executive branch officials. When Congress demands such information, it must explain its need carefully and convincingly."
Not knowing what or who was under investigation would limit Jordan's ability to fulfill this requirement.
