It is
US Code
TITLE 18 > PART I > CHAPTER 115 > § 2381
Treason
Whoever, owing allegiance to the United States, levies war against them or adheres to their enemies, giving them aid and comfort within the United States or elsewhere, is guilty of treason and shall suffer death, or shall be imprisoned not less than five years and fined under this title but not less than $10,000; and shall be incapable of holding any office under the United States
Methinks this applies to Hanoi John and Hanoi Jane as well, among others of their ilk. Is there a Statute of Limitations on treason?