Adding Dual Citizenship to Nexus
You can update existing documents in GOES (ie passport renewal). I had to go to YYZ T1 office a few weeks back, as I was a Canadian NEXUS member who recently acquired US citizenship and had to add my US passport to the system. So now I'm a dual citizen. Wasn't sure how that was going to work with Nexus...
I arrived at 8am after coming from a connecting flight... there were only CBSA officers there, no CBP. They took a photocopy of my new US Passport, and said they would have CBP enter it into the system later in the day. My old Nexus card was taken from me, as I would have to get a new card that showed my US citizenship. "US trumps everything" I was told. Kind of a bummer, since I was about to board a flight to the US and wouldn't be able to use my Nexus for this trip.
I was asked to login to GOES and order a new card once my new passport details were on file. I was advised to report the old card as "damaged" (they said it would be less chance of being asked to go to a new interview than if I report as lost or stolen). Had to pay a $25 USD fee and got my card within 2 weeks. The new card shows my citizenship as US, nothing about my Canadian citizenship. I assume that won't be much of an issue, but will find out when I'm travelling again next week.