I guess it probably depends on your original nationality. If you are American, then there is no problem since American citizens are entitled to be NEXUS member without Canadian citizenship or residency. In my case, however, I was told that I was eligible to be a NEXUS member only as PR of Canada. But now I'm not a PR any longer, so I need a new card that says I'm Canadian.This is so confusing. I went into Vancouver and was told that I don’t need a new card even though I was giving up my old citizenship and acquiring Canadian. They just took a copy of my passport and nexus and said it would be updated in 5 business days. I guess I’ll check in a week and go in again...
I'm not buying the story 100%, since the card did not report anywhere that I was a PR, so I don't see much of a difference between not reporting my PR (which was the condition allowing me to participate to the program) and not reporting my Canadian citizenship. I don't mind having the card re-printed, what I don't understand is why I couldn't use the old card in the meantime. I just hope I get the new card quickly.