A couple of thoughts on this. First, you were lucky that at ATL you were flying on Delta internationally on Delta metal, which is the only reason you could have done this. I was on a DL codeshare flight recently (KLM metal) and tried to check bags at DL domestic for the international flight and was told I can only do this at the international terminal even though it was DL codeshare flight. There are several other instances of this also I read about this on travel blogs once I checked this after the fact and have since learned my lesson. Riding the inter-terminal bus (outside security) is not a fun way to start a vacation. Second, Many years ago when I had a green card (plastic laminated by the issuer) I had an edge start to fray slightly (think 1/8" to 1/4" at most) and it as nowhere near the actual card itself. Going through DTW from TPE I hit CBP there and the border agent looked at my card and told me I needed to get it replaced as it was "damaged". To my own fault, I kind of filed it away in my mind. At that time I was traveling fairly regularly to Asia (one trip every 4 weeks or so) and used DTW as a gateway due to convenience for NWs flights. It must have been 2 trips later and I was coming through DTW CBP again, sleepy as usual from the 20+ hrs of travel coming back from SE Asia, and while waiting for the agent to process me I heard a voice say "I thought I told you to get this card replaced?" That woke me up, and I couldn't believe my luck to get the SAME CBP agent out of hundreds who work there. Needless to say he then put a note in the system and politely told me that if I came into the US again on that green card I would be detained and spend alot of time explaining myself. I went in to get my replacement card 2 days later. This was completely on me but something I thought was minor was obviously not for them. I think in ATLawyer's case the frustration is the DL agent over-riding what CBP said, which is the fact the passport was still acceptable. Unfortunately, regardless of the airline you find folks like this from time to time. Maybe a bad day or they just hate their job. Fortunately for me, most of the airlines I travel it is the exception and not the norm.