Traffic officer Andy Holden is claiming sex discrimination because female officers are allowed to wear jewellery.
The 40-year-old police motorcyclist says both formal and informal requests to wear the stud have been refused. The officer, who has been commended for bravery, was first ordered to remove his stud seven years ago but began a grievance procedure.
PC Holden, who is married to another police officer, has 15 years' service. He said most colleagues supported his cause, although some questioned his sexuality when they saw the earring. His case, which will be heard in February, is being backed by the Police Federation.