Okay, now that Ted has explained this in the Madison, WI airport --
If both mouths of the wormholes open onto the same universe (and if the wormhole doesn't destroy itself via quantum fluctuations), then I think the best guess is that the Novikov self-consistency principle holds.
From what I understood, what you mean is that general relativity implies that the Novikov self-consistency principle holds -- that is, self-consistency is already implicit in general relativity.
But it sounds like it's also a falsifiable hypothesis. The "radical rewrite hypothesis" isn't logically inconsistent -- it's just forbidden by general relativity (which is to say, evidence for it would force a revision of general relativity).
You set up an experimental apparatus for shooting a billiard ball through a wormhole. The billiard ball is meant to emerge from the other end in time to strike itself before it goes in, keeping it from going in -- the grandfather paradox in the lab.
Kip Thorne's calculations, according to Ted, say that general relativity demands that what you see is this: the ball shoots toward the entry wormhole. Just before it hits, its future self emerges from the exit wormhole and strikes it a *glancing blow* -- just enough to drive it into the entry wormhole at such an angle that it can emerge, strike itself a glancing blow and clatter to the ground.
Given that I can't follow the math, it seems natural to me that this would be already implicit in the assumptions of general relativity.
Consider the following result:
So you get your experimental apparatus set up. You write on your billiard ball "Professor Thorne was here 8/23/2045" with a Sharpie. Then you launch it through the wormhole.
But before it can enter, another billiard ball flies out of the exit wormhole, strikes the first a solid blow, and both of them clatter to the floor of the lab.
Now there are two billiard balls on the ground, both of which say "Professor Thorne was here 8/23/2045" in black magic marker.
I can imagine, even if I can't follow the math, where this result would be problematic from the point of view of all kinds of principles of physics -- conservation of mass/energy and of momentum, for instance (though maybe the wormhole mechanism somehow makes up the differences there?)
The next question is, though: if we did in fact actually observe this, could we make up an elegant, naturalistic theory that would account for it?
I expect we could.
And I expect one camp of interpreters would say "there are two balls, one sent by the Professor Thorne of a parallel universe, who is wondering where his ball went, one sent by this Prof. Thorne" and the other would say "there are two balls, one from a timeline which was erased by its successor timeline, leaving only this ball as evidence that it ever existed. When did it exist? Why, three beta-seconds ago along the t-beta time axis, of course."
Are there experiments which could determine which of these interpretations is correct?
Well, if Prof. Thorne is standing there holding two balls and a paper airplane comes out of the wormhole exit with a note saying "what happened to my ball?" we would assume the former, but I'm not sure *that* makes any sense with the original setup (that there is only one entry and exit for the wormhole, and they're both in this Prof. Thorne's lab).
So this is the point at which I think I *would* actually need to understand the math to say anything meaningful. It's easy from this point on to postulate things that sound sensible but are in fact nonsense, *given* the (unclear to me) constraints under which the experiment was set up.
But nothing has yet convinced me that Prof. Thorne holding two billiard balls *cannot happen*, nor that if it did *no scientific explanation would be possible*, though I am perfectly willing to believe that it would force a vast revision of physics-as-we-know-it.