Starfleet uniform code

The Starfleet uniform code was the group of Starfleet regulations governing the proper manner of wearing Starfleet uniforms. 

The uniform code of the 23rd century Federation Starfleet permitted some personalization of the uniform. Lieutenant Uhura and Dr. Ann Mulhall wore earrings. Scotty wore a kilt as part of his dress uniform in the 2260s. Native American personnel were permitted to wear traditional jewelry with their duty uniforms in the 2270s. 

In the 24th century, Worf was permitted to wear his baldric as part of his duty uniform, but Ro Laren was initially forbidden to wear her Bajoran earring as part of hers. Although Ro was eventually permitted to wear her earring, Bajoran crewmembers on board some other starships were not allowed to do so. In addition, elaborate headbands and jewelry were in violation of the dress code, though simple headwear, such as simple headbands and Ferengi headdresses were permitted. (, and more)