Players Wearing Non-Compulsory Equipment
On August 25, 2003, FIFA issued Circular #863, regarding the legality of players wearing non-compulsory equipment.
Law 4, Players’ Equipment (Jewelry)
March 17, 2003
Law 4 (The Players' Equipment) states very clearly that "A player must not use equipment or wear anything which is dangerous to himself or another player (including any kind of jewelry)."