There is an ancient martial arts tournament called the kumite that takes place on an isolated island. This tournament brings together the greatest fighters of the various mortal realms to fight each other in IMMORTAL KONFLICT!!! Fighters include cyromancers, undead, fire-breathing ninjas, talking dragons, and monks. The combatants must fight to the death, with the winner gaining glory and honor for their respective realms.
Individuals who wish to stop this tournament from taking place or combatants wishing to cheat may try to Sabotage it by killing people before fights take place. Therefore, all participants are protected by a thin shield that covers their skin. This shield is unseeable, and is completely resistant to projectiles. Bullets, arrows, etc are unable to pierce this shield. However, physical blows such as punches and kicks are completely effective. This is to ensure that the fights are fair between combatants.
How could this shield be resistant to projectile weapons, but not be resistant to human contact?