Army Regulation 670-1, Wear and Appearance of Army Uniforms and Insignia, is the governing authority for the wear of Army uniforms. Paragraph 28-18 governs the wear of the United States Flag on Army Uniforms.
The flag may only be worn on the utility and organizational uniforms (such as the camouflage BDU). The flag may only be worn during joint-duty and multinational deployments. When the servicemember returns to home station, the flag must be removed. (Guide Note: A message went out in February 2004 changing this restriction, and making the U.S. Flag a mandatory uniform component for all soldiers, effective October 1, 2005).
Chapter 1, Title 4, United States Code, provides for the design of the U.S. flag and specifies the colors as red, white, and blue. Colors other than red, white, and blue violate the U.S. Code; therefore, subdued-colored flags are not authorized for wear. Joint commanders have to make the decision as to whether or not the wear of a full-color flag, for morale purposes, is more important than having all aspects of the uniform camouflaged.
When approved for wear, the full-color U.S. flag cloth replica is sewn 1/2 inch below the right shoulder seam of the temperate, hot-weather, enhanced hot-weather, and desert BDU; the BDU field jacket; and the cold-weather uniform. The flag is worn on the right shoulder, because, in the military, the "place of honor" is to a military member's right.
The full-color U.S. flag cloth replica is worn so that the star field faces forward, or to the flag’s own right. When worn in this manner, the flag is facing to the observer’s right, and gives the effect of the flag flying in the breeze as the wearer moves forward.
The rule dates back to the Army's early history, when both mounted cavalry and infantry units would designate a standard bearer, who carried the Colors into battle. As he charged, his forward momentum caused the flag to stream back. Since the Stars and Stripes are mounted with the canton closest to the pole, that section stayed to the right, while the stripes flew to the left.