According to one aspect of the teachings herein, a set of rules for transmitting Downlink Control Information (DCI) messages containing Transmit Power Control (TPC) commands is known to a wireless communication network (10) and to any number of wireless devices (20) supported by network (10). A device (20) receiving a given TPC DCI message knows the uplink channel(s) to which the received TPC command(s) are to be applied based on interpreting the given TPC DCI message according to the known rules. The rules may be defined as internal within the DCI format, such as bits, states or code points. Additionally, or alternatively, the rules may be defined according to external attributes for DCI message transmission, such as whether the DCI message is transmitted on a Physical Downlink Control Channel, “PDCCH” or on an enhanced PDCCH, “ePDCCH”.