According to its new code redemption FAQ, coupons "are intended for use by the purchaser" and no one else. As such, you'll need to redeem the codes through your GeForce Experience app account, which then links to the relevant store. Unfortunately, it'll also perform a hardware check "to ensure that the coupon code is redeemed on the system with the qualifying GPU," the FAQ states. NVIDIA didn't say that it's tied to one particular card, so presumably, you could give or sell the code to a user with the same model.
NVIDIA may be trying to stop a recent fiasco that allowed users to order a GTX 1070, get a Gears of War 4 code, then return the card, scoring the game for free. However, some Reddit users think that it could also be an NVIDIA ploy to get users signed up for GeForce Experience, an app that many PC gamers despise. Another theory is that publishers asked NVIDIA to implement the checks to kibosh shady discounts. Given the attention it's getting, however, it may actually provoke gamers to check out this whole discount code thing, proving once again the power of the Streisand effect.