According to the FCC Web site


Operations
Equipment
Territorial Limits
Linear Amplifier Ban
Antennas
Ten Codes

47 CFR 95 Subpart D prescribes all operating requirements which apply
to CB. General system technical details and major operational regulations
are highlighted below.

Equipment


You must use an FCC certificated CB transmitter at your CB station.
You can identify an FCC certificated transmitter by the certification label
placed on it by the manufacturer.

Territorial Limits


You may operate your CB unit within the territorial limits of the
fifty United States, the District of Columbia, and the Caribbean and Pacific
Insular areas ("U.S."). You may also operate your CB on or over any other
area of the world, except within the territorial limits of areas where
radio-communications are regulated by another agency of the U.S. or within
the territorial limits of any foreign government. You may also be permitted
to use your CB unit in Canada subject to the rules of Industry Canada.
Travelers to the U.S. may operate a CB unit within the U.S. as long the unit
is FCC certificated.

Linear Amplifier Ban


Users may not raise the power output of their CB units. That would be
unfair to the other users sharing the channel by raising the level of radio
noise. You must not attach a "linear," "linear amplifier" or any other type
of power amplifier to your CB unit, Moreover, you must not modify your CB
unit internally. Doing so cancels its certification and you forfeit your
authorization to use it.