NY Times Columnist David Pogue saw “National Treasure 2” and felt mis-led by the trailer, which seemed to contain bits left out of the final cut. Pogue asks:

Just how different can a trailer be without becoming false advertising?
In this case, those lines from Riley made the movie seem funnier than it was, the president’s line made the dramatic stakes seem higher than they were, and the scenes at the Lincoln Memorial made the historical conspiracy seem more ingenious than it was (historical clues hidden right under our noses!). I can say with confidence that some of those elements played a part in my wanting to see the movie.
Rearranging scenes in the trailer is one thing. But what about this business of putting stuff in the trailer — a *lot* of stuff — that isn’t in the movie at all? If they can get away with “National Treasure”-style misrepresentation, what’s to stop other moviemakers from putting special effects, witty lines, exotic locales and hot-looking actors into *their* trailers, just to get us to go to a movie that doesn’t have any of those things?

So how to advise your movie trailer producer client to avoid false advertising? Draft a suitable disclaimer for the trailer. I’ll get you started:
“Objects in the trailer may appear more entertaining than they are”
“Movie subject to change without notice”
“This trailer contains movie and movie by-products”
“Any discussion of this trailer without the expressed written consent of Major League Baseball is strictly prohibited”
“Contents of movie may settle during shipment”
If you’re stuck with coming up with a suitable disclaimer, here’s a list to consult.
BUT SERIOUSLY, 43(B)log reviews this question and opines that it is certainly within the realm of possibility that because a trailer implies that the footage shown is in the movie being advertised, that the trailer as Pogue describes it is explicitly false, and that a colorable action may lie.
And as long as we’re free associating about sharp movie practice: some of you may recall that in 1984 Eddie Murphy was the hottest comedy star around. Dudley Moore made a movie called “Best Defense” and the advance word was that it was horrible. Reportedly, after major filming was finished, Murphy was brought in and twenty minutes of film was made and added to the film, which was then advertised as a Dudley Moore and Eddie Murphy comedy, even though they never appeared in the same frame. Hilarity ensued.