John Napier Tye, in a guest column for the Washington Post:
Issued by President Ronald Reagan in 1981 to authorize foreign intelligence investigations, 12333 is not a statute and has never been subject to meaningful oversight from Congress or any court. Sen. Dianne Feinstein (D-Calif.), chairman of the Senate Select Committee on Intelligence, has said that the committee has not been able to “sufficiently” oversee activities conducted under 12333.
Unlike Section 215, the executive order authorizes collection of the content of communications, not just metadata, even for U.S. persons. Such persons cannot be individually targeted under 12333 without a court order. However, if the contents of a U.S. person’s communications are “incidentally” collected (an NSA term of art) in the course of a lawful overseas foreign intelligence investigation, then Section 2.3(c) of the executive order explicitly authorizes their retention. It does not require that the affected U.S. persons be suspected of wrongdoing and places no limits on the volume of communications by U.S. persons that may be collected and retained.
The means of intelligence gathering have changed substantially since 1981, but this loophole remains open.