I also found that the United States Federal Trade Commission standards for "Made in USA" labelling only require that
the product be "all or virtually all" made in the U.S.
Under California's state laws, an product for sale in California cannot be labeled as “Made in U.S.A.” “when then merchandise or any article, unit, or part thereof, has been entirely or substantially made, manufactured, or produced outside of the United States.”
Incidentally, my recently purchased SOG powerlock's packaging displayed no country of origin markings. There are no markings on the SOG tool either.* The paperwork inside the SOG's package, however, clearly states "Made in USA."
I checked the paperwork that came with a few leathermans, and I found no country of origin info on the leatherman paperwork.
*EDIT: The SOG is clearly stamped "SOG USA" on the pliers. Oddly enough, you can't see the "USA" when the SOG is fully opened or fully closed, but it's clearly visibly between opened and closed positions. (The gears cover the "USA" stamp when it's fully opened, and the handles cover the "USA" stamp when it's fully closed.)