From the Acton-Boxborough Youth Soccer Board of Directors - Please adhere to the following policy:

All jewelry must be removed prior to the start of a game. All players will be checked for jewelry, watches, and barrettes. In the event that a medical alert bracelet must be worn, the coach may use athletic tape to secure the bracelet securely against the player's wrist. Bandages over starter earrings are not an acceptable alternative to removing the earrings, as the earrings may still be accidentally ripped out by another player. We apologize for the inconvenience, but please know that this policy is in place to protect the safety of all players on the field.

From Everything Soccer - The Nitty Gritty on Soccer Safety:

Earrings in particular are prone to being torn from earlobes when contact is made with a soccer ball. By removing these pieces of jewelry and other items of this nature, you can help prevent injuries to yourself that could be disfiguring. If you are considering getting piercings and you play soccer, you may want to consider planning to have your piercings done when the soccer season is over.