Treason and Passport Revocation Act of 2015 Amends the federal criminal code to include an organization that the Department of State has designated as a foreign terrorist organization as an enemy of the United States for purposes of the crime of treason. Amends the Passport Act of 1926 to: (1) prohibit, with a discretionary exception for emergency or humanitarian reasons, the Department of State from issuing a passport or passport card to an individual who is a member of, or affiliated with, a foreign terrorist organization; and (2) require the Department to revoke a passport or passport card previously issued to any such individual. Authorizes the Department, before revocation, to: (1) limit a previously issued passport or passport card to only return travel to the United States, or (2) issue a limited passport or passport card that permits only return travel to the United States.