It's the dog tag. The dumb jock is unaware that the dog tag passed by his father actually contained mind-controlling chip that will emit command that his brain unable to resist upon wearing. Just a standard military procedure to create a bunch of obedient, well-disciplined, ruthless drone. Taking it off is the only way for the effect and control to wear off and people with them tend to be very protective and defensive about it, plus the subconscious alteration already imbedded on the tag will create irrational fear, guilt and all sorts of feeling if their mind ever think or swayed to take it off.
Yet the new gens of controller behind the tags and drones created by it are unafraid to insert their personality a bit more. Chris apparently got a gooner of a controller