Protection of Uniforms
Clause 4. Prohibition of Alteration or Imitation.
a.No alteration of, or additions to, the official uniforms, as described in the official publications, or the rules and regulations covering the wearing of the uniform and the proper combinations thereof on official occasions, may be authorized by any Scouting official or local council or any local executive board or committee, except the Executive Board of the Boy Scouts of America after consideration by the Program Group Committee. b.Imitation of United States Army, Navy, or Marine Corps uniforms is prohibited, in accordance with the provisions of the organization's Congressional Charter.
Hence, the no "camo" regulations that most people cite. (without knowing that this is the source)
As far as the orginal question:
Clause 2. The official uniforms authorized as evidence of official relationship to the Boy Scouts of America shall be those approved by action of the Executive Board of the Boy Scouts of America from time to time, as illustrated and correctly described in the handbooks, catalogs, and other official publications of the Boy Scouts of America.