If you read the Mutcd - it is not a LAW it is a standard for traffic control devices and signage. It states the arm should be long enough to effectively restrict motorized vehicles. Does not say we can not have the Welcome Home sign. It does say the mechanism must be at least 2ft. behind the edge of the curb. Read the MUTCD
http://mutcd.fhwa.dot.gov/pdfs/2009/part2b.pdf