Can a coach stop the soccer game or only the referee can?

Answer 1

The referee is the sole judge of time in the match. The referee is the only one who has the power to end the game because time has expired.

Now, speaking about during play, the same rule exists. The referee is the only one who has the authority to stop play or terminate the match early for any reason. Now, assuming that a coach leaves the field when tournament rules require that a rostered coach be present at all times during the game (as almost all youth matches do), the referee would be forced to terminate the match early due to insufficient people on that team. (The insufficiency comes from the fact that there are not enough coaches (one) to continue/start the match.)

The referee would stop play and then declare the match over. His match report would contain specific details of the event and note that the match was terminated early. The referee would also report the score at the time of termination. The referee has no power to determine a winner or a forfeiture. His only authority regarding outcome of the match is that he sends his detailed report to the league coordinator. The league would then decide what actions to take (i.e. the winning team or forfeiting team, whether the match should be played again, or if disciplinary action needs to be taken against the team/coach).

This can be found in The Laws of the Game, under Law 5 - The Referee:

Powers and DutiesThe Referee:

• enforces the Laws of the Game.
• ...
• acts as a timekeeper and keeps a record of the match.
• stops, suspends, or abandons the match, at his discretion for any infringements of the Laws.
• stops, suspends, or abandons the match because of any outside interference of any kind.
• stops the match if, in his opinion, a player is seriously injured and insures that he is removed from the field of play. An injured player may only return to the field of play after the match has restarted.
• ...
• indicates the restart of the match after it has been stopped.
• provides the appropriate authorities with a match report, which includes any information on any disciplinary action taken against players and/or team officials, and any other incidents that occurred before, during, or after the match.

There are obviously more responsibilities/powers that the referee has, but the ones listed in the Laws that are pertinent to this question are the ones listed here.

Source: FIFA Laws of the Game 2012/2013 - Law 5: The Referee (pages 24-25).

Additional interpretations of the roles of the referee can be found on pages 69-73.

Answer 2

well I'm not to sure really, probably not, but i am not to sure. a very intresting question. lol