Yes, sure. No one said that the nail makers would be guaranteed a market for their nails. However it might be better for the boot makers to renegotiate their contract? And what is the cost of screwing over your local supplier? Maybe local public services will prefer boots entirely made in $your-country? Economy is way more complicated than always chasing after the biggest short term profits.
Of course - maybe they will :) and maybe they won't. Which is way less certain than saying "they [the shoemakers] NEED to source a local supplier", as you wrote.
The key thing here is that if I buy boots cheaper by 1/4 (thanks to partial outsourcing), I will spend the 1/4 I saved by going to a barber. Or a local restaurant. Or by buying doughnuts at a local bakery. So - speaking of economy to which there's more than meets the eye - these are local suppliers too, indirectly benefiting from the fact that local shoemaker imported nails.
