Hmm...I always thought the argument ran like this:
Soldiers have to swear an oath of allegiance, said oath being their permission to be subject to military law. That oath is a solemn promise, similar in status to the promise you make to tell "the truth, the whole truth, and nothing but the truth" in a court of law. Therefore, Sheehan is perfectly within her rights to advocate US withdrawal from Iraq, she can protest and demonstrate to her hearts content, but if she tries to persuade a US soldier from serving she is, in affect, inciting them to perjure themselves, which of course is illegal.
Have I got this right?
TITLE 18 > PART I > CHAPTER 67
§ 1381. Enticing desertion and harboring deserters
Whoever entices or procures, or attempts or endeavors to entice or procure any person in the Armed Forces of the United States, or who has been recruited for service therein, to desert therefrom, or aids any such person in deserting or in attempting to desert from such service; or
Whoever harbors, conceals, protects, or assists any such person who may have deserted from such service, knowing him to have deserted therefrom, or refuses to give up and deliver such person on the demand of any officer authorized to receive him—
Shall be fined under this title or imprisoned not more than three years, or both.
TITLE 18 > PART I > CHAPTER 115
§ 2387. Activities affecting armed forces generally
(a) Whoever, with intent to interfere with, impair, or influence the loyalty, morale, or discipline of the military or naval forces of the United States:(1) advises, counsels, urges, or in any manner causes or attempts to cause insubordination, disloyalty, mutiny, or refusal of duty by any member of the military or naval forces of the United States; or
(2) distributes or attempts to distribute any written or printed matter which advises, counsels, or urges insubordination, disloyalty, mutiny, or refusal of duty by any member of the military or naval forces of the United States—
Shall be fined under this title or imprisoned not more than ten years, or both, and shall be ineligible for employment by the United States or any department or agency thereof, for the five years next following his conviction.
TITLE 18 > PART I > CHAPTER 115
§ 2388. Activities affecting armed forces during war(a) Whoever, when the United States is at war, willfully makes or conveys false reports or false statements with intent to interfere with the operation or success of the military or naval forces of the United States or to promote the success of its enemies; or
Whoever, when the United States is at war, willfully causes or attempts to cause insubordination, disloyalty, mutiny, or refusal of duty, in the military or naval forces of the United States, or willfully obstructs the recruiting or enlistment service of the United States, to the injury of the service or the United States, or attempts to do so—
Shall be fined under this title or imprisoned not more than twenty years, or both.
(b) If two or more persons conspire to violate subsection (a) of this section and one or more such persons do any act to effect the object of the conspiracy, each of the parties to such conspiracy shall be punished as provided in said subsection (a).
(c) Whoever harbors or conceals any person who he knows, or has reasonable grounds to believe or suspect, has committed, or is about to commit, an offense under this section, shall be fined under this title or imprisoned not more than ten years, or both.