A tag for RFID applications and the like comprises an antenna supported on a dielectric substrate and having a first electrical length suitable for communication as a transponder. A selectively removable conductive shunt causes the antenna to assume a second electrical length which impedes transponder communication. Applications of the tag include tag-bearing products that are non-transmissive beneath surrounding packaging, and state machines that change between transmissive and non-transmissive states with selective shunting of the antenna. A method for enhancing an RFID tag for selective operation is also provided.