This implies that a goal is not scored unless the ball has wholly crossed the goal line between the goal posts and beneath the crossbar. Soccer is a sport designed to give skill the advantage over force. The Laws permit physical contact, but limit it to non-dangerous forms. Other kinds of contact are illegal and are penalized by the referee. Careless, reckless, or unnecessarily hard contact by a player on his opponent does not become legal simply because the ball was struck in the process.
Referees penalize only clear infringements.
In fact, they are specifically instructed not to penalize doubtful or trifling breaches of the Laws. This is in sharp contrast with many sports popular in the United States, in which spectators expect the referee to stop play for all sorts of trifling violations. A knowledgeable spectator will understand and appreciate why, for example, a referee ignores inconsequential jostling between opponents and allows the game to precede uninterrupted. Instead, arm signals are used to indicate how the game is to be restarted. In unusual circumstances, the referee may explain a particular decision to the players.