Phone cloning is outlawed by the Wireless Telephone Protection Act of 1998, which prohibits:
knowingly using, producing, trafficking in, having control or custody of, or possessing hardware or software knowing that it has been configured to insert or modify telecommunication identifying information associated with or contained in a telecommunications instrument so that such instrument may be used to obtain telecommunications service without authorization.
The effectiveness of phone cloning is limited. Every mobile phone contains a radio fingerprint in its transmission signal which remains unique to that mobile despite changes to the phones ESN or MIN. Thus, cellular companies are often able to catch cloned phones when there are discrepancies between the fingerprint and the ESN or MIN.