Colorado Statute:
42-3-202.
Number plates to be attached.
http://198.187.128.12/colorado/lpext.dll/Infobase4/63d1b/64836/64838/64af4/64b14?fn=document-
http://www.kscourts.org/ca10/cases/2006/02/05-3167.htm
(court case)
(1) Number
plates assigned to a
self-propelled vehicle other
than a motorcycle or street rod
vehicle shall be attached
thereto, one in the front and
the other in the rear. The
number plate assigned to a
motorcycle, street rod vehicle,
trailer, semitrailer, other
vehicle drawn by a motor
vehicle, or mobile machinery or
self-propelled construction
equipment shall be attached to
the rear thereof. Number plates
shall be so displayed during the
current registration year,
except as otherwise provided in
this article.
(2) (a)
Every number plate shall at all
times be securely fastened
to the vehicle to which it
is assigned, so as to prevent
the plate from swinging, and
shall be horizontal at a
height not less than twelve
inches from the ground,
measuring from the bottom of
such plate, in a place and
position to be clearly visible,
and shall be maintained free
from foreign materials and in a
condition to be clearly legible.
(b) A
person shall not operate a motor
vehicle with an affixed device
or a substance that
causes all or a portion of a
license plate to be unreadable
by a system used to
automatically identify a motor
vehicle. Such a device includes,
without limitation, a cover that
distorts angular visibility;
alters the color of the plate;
or is smoked, tinted, scratched,
or dirty so as to
impair the legibility of the
license plate.
(3) (a) A
person who violates any
provision of this section
commits a class B traffic
infraction.
(b) A
person who violates paragraph
(b) of subsection (2) of this
section commits a class A
traffic infraction and shall be
punished by a fine of one
hundred dollars.
California
from: http://ktmtalk.com/index.php?showtopic=205236&st=15&#entry1718874
4851. Every license plate
shall have displayed upon it the
registration number assigned to
the vehicle for which it is
issued, together with the word
"California" or the abbreviation
"Cal." and the year number for
which it is issued or a suitable
device issued by the department
for validation purposes, which
device shall contain the year
number for which issued.
5201. License plates shall at
all times be securely fastened
to the vehicle for which they
are issued so as to prevent the
plates from swinging, shall be
mounted in a position so as to
be clearly visible, and shall be
maintained in a condition so as
to be clearly legible. The rear
license plate shall be mounted
not less than 12 inches nor more
than 60 inches from the ground,
and the front license plate
shall be mounted not more than
60 inches from the ground...
24601. Either the taillamp or a
separate lamp shall be so
constructed and placed as to
illuminate with a white light
the rear license plate during
darkness and render it clearly
legible from a distance of 50
feet to the rear. When the rear
license plate is illuminated by
a lamp other than a required
taillamp, the two lamps shall be
turned on or off only by the
same control switch at all times