Here's what section 3 says:
No person shall be a Senator or Representative in Congress, or elector of President and Vice President, or hold any office, civil or military, under the United States, or under any State, who, having previously taken an oath, as a member of Congress, or as an officer of the United States, or as a member of any State legislature, or as an executive or judicial officer of any State, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. But Congress may by a vote of two-thirds of each House, remove such disability.
But for the purposes of the Treason Clause, and I suspect of section 3, the test isn't simply whether the actions help the enemy, or help the enemy through improper means, or help the enemy through improper means with the knowledge that they will help the enemy. If Kerry's purpose was not to help the North Vietnamese, but to help the United States or to help maintain U.S. compliance with its own laws and policies related to military conduct, then he's not covered. And I have no reason to think that Kerry's purpose was indeed anything other than to help the United States, whether or not his actions in pursuit of that purpose may have been misguided or excessive.
There has been quite a bit of jabbering on the conservative side of the blog-o-sphere concerning John Kerry's eligibility for the Presidency based upon his anti-war actions while still a U.S. Navy officer. Well, sorry folks, but it doesn't look like you can hang him out to dry for treason quite yet. However, there has been some more ruffling of feathers over Kerry's comments about a U.S. soldier's blood is worth it only under a U.N. flag.