An RFID tag has an antenna to receive a configuration signal, and a circuit with a controller that can configure the RFID circuit responsive to the configuration signal. Configuring is such that the tag backscatters by impressing data either on the carrier frequency, or on a subcarrier in addition to the carrier signal, depending on the configuration signal. In the event of a subcarrier, the tag controller may optionally further determine a frequency of the subcarrier from the configuration signal. The tag may then be configured to backscatter differently, upon receiving a different configuration signal. A complementary reader transmits the configuration signal, thus imparting an operating parameter. The reader has an interface to receive an input indicative of a present geography, and a lookup table for determining an operating parameter based on the present geography. In one embodiment, the operating parameter is determined from regulations at that geographic location.