Is there a law that if you come am hour before your flight and they tell you that you missed your flight

I work for the airlines and they all have the same policy. 10-15 min before departure time they can close the flight out and you can miss it. They can't and won't close it out before then. Hope that helps.

For international flights, it's suggested to arrive at least two hours before the scheduled departure time. It's summer now, so that's also a good idea for domestic flights. If the flight is delayed and you receive a notification; it's still suggested that you arrive at least one hour before the originally scheduled time - in case the delay is lifted.