There is no problem with a player passing the ball back to the goalkeeper. However, according to FIFA Laws of the Game, if a player deliberately passes the ball to their goalkeeper using their foot (not a mis-kicked ball), then the goalkeeper may not use their hands to play the ball. They may still play the ball with any other part of their body, but cannot use their hands. The punishment for violating this rule is an indirect free kick for the attacking team. To emphasize - this is NOT a "handball" and a penalty kick is not the result. It is a technical infraction punished with an "indirect" free kick. A wall may be set. (Note: Players MAY stand on the goal line between the goal post, even if the ball is less than 10 yards from the goal, and the kick may not be taken from any closer than 6 yards out from the goal.) Within LWYSA, this rule is enforced according to FIFA laws of the game beginning at U-10. For our U8-U9 games (U7 does not have a goalkeeper), if a ball is passed to the goalkeeper and the goalkeeper uses their hands, the referee should pause play, explain the rule, and then allow play to continue. The referee should only award a free kick to the attacking team after the rule has been explained and after the infraction has been repeated.
Note:Coaches are reminded that the U7-U9 ages are intended to be "instructional". Because this rule can be confusing, we do not "penalize" the player for an infraction. Instead, we try to "teach" the rule.