According to FIFA the ball is considered out of play when either of these two conditions exist:

• It has wholly crossed the goal line or touch line whether on the ground or in the air
• Play has been stopped by the referee

The key word here is "wholly." The entire ball must completely clear the goal line for a goal to be scored. The same thing applies to an out of bounds situation. The entire ball must cross the touch line before it is considered out of play.

Note that the position of the player is never mentioned. That is because it has no bearing on the call. A player can actually be "out of bounds" and still kick a ball that is in bounds.