ridge, this would be a terrible idea and would lead to authorities entering homes as they please in the name of a "safety check "
the only reason i would consider a gun buyers card is im cheap . pay 10 bucks once every 2 years -vs- 10 bucks each transaction . this would also help private sales as well . if your at all worried about a potential buyer just ask if he has a card , if he/she has said card then you know they are good to go . of course this would not prevent fake cards , or those that have broken a law after they have gotten the card .