Whether a carrier needs interstate authority depends on a number of things but begins with the threshold question whether any of the shipments it is handling are in "interstate commerce." What constitutes "interstate commerce" can sometimes be a difficult question to answer with certainty. As a general rule, all legs of shipments moving between different states or between a state and a foreign country without "coming to rest" (in itself a complex determination) are considered to be in "interstate commerce." A motor carrier performing any part of the transportation services on such shipments --even if that carrier's particular services are performed entirely within one state--must (unless an exception applies) have appropriate interstate authority.
Since the SAFETEA-LU Technical Corrections Act of 2008, interstate authority may be required regardless of the size of the motor vehicle used for transportation. So motor carriers using smaller vehicles, such as delivery companies and messenger services, are also subject to this concern. Carriers who believe they are subject only to state regulations because they never leave their home state should review whether their services include handling of shipments in "interstate commerce." If so, they should determine whether an exception applies, or obtain the required authority and as needed come into compliance with the Federal Motor Carrier Safety Laws and the Federal Motor Carrier Leasing Regulations.