This is classed as dangerous play, and therefore can be penalised by by an indirect free kick. This is because it does not permit opponents to challenge for the ball safely.
What? The ball could be headed off the player's neck. Or it could be discharged with a legal shoulder charge. Besides which, anyone cheeky enough to try to get away with this type of play deserves to get their head taken off by a bicycle kick "attempting" to get the ball. The players will sort out this twit without any interference by the referee.
This is no different from the situation of a player who hops down the field with the ball between his ankles, who be guilty of Dangerous Play as it makes it unsafe for an opponant to challenge for the ball. It is similar to the player bringing his head down excessively low to challenge for the ball as a header. This is an equally, if not moreso, unsafe practice. Dangerous Play, IFK. Next question.
Why would you want to do that anyways? you would be faster running with it by your feet then balancing it on your head lol
I've had this same question in my clinics many times and I always ask in return, "Why would you do that?" One kid stumped me -- "I like being kicked in the head!" To each his own...
When you award an indirect free kick for dangerous play then one of two things has happened: 1) A player has endangered another player without making contact with that player 2) A player has endangered himself/herself with his/her actions The "ball on the back of your neck" situation is obviously a player endangering himself/herself. A more common example occurs when a player falls forward onto a stationary ball landing on top of the ball and makes no effort to move from being on top of the ball. Crowdie
For me, it's not really in the spirit of the game. I would be more inclined to see it as Unsporting Behavior. A ref in our area had a black player with a large Afro trap the ball on the top of his head. The ball stayed nestled in his Afro hair style and he started to move downfield. The ref (correctly in my opinion) stopped play for Unsporting Behavior. Would we let a player hop down the field with the ball between his knees? Would we let a player run with the ball under his shirt or carried in her shirt? It's just not in the spirit of the game.
It's first and foremost Dangerous Play. Whether it warrants a caution for USB is up to the referee, and depends on the situation. Dangerous Play, again. An interesting one. Certainly USB - but the restart? I'd be inclined to call it as Handball, regarding the shirt as an extension of the hands. That's assuming that the player used their hands to manipulate the shirt to catch the ball. If not, just the IFK for stopping play for the caution.