Even a pardon won't allow you to cross anymore.

I too am a NEXUS card holder who has cross by both air and truck many times. ITS random but I have had myself pulled in and the truck completely searched quite a few times.
Got nothing to hide..... you have nothing to worry but lose a bit of time. Still works for me.

PS the DUI works both ways. You cannot enter Canada or the USA with a DUI record.
Thanks