My Fiancé started working at his current job about a week and a half ago. He asked about taking of four days for the wedding (which is on August 1) and they told him today that he could not have any of the days off and if he took them off anyway, he would face disciplinary actions. How can they do this? What can they actually do to him if he takes off? If they fire him for taking off for his own wedding, is there anything he can do about it?

1) The company is within its rights to punish him for missing work. I'm not saying they are not wrong for that, but they still could.
2) He should have negotiated this BEFORE starting the job. It would have made things much simpler.
3) Good luck. Usually the first time you are disciplined it is only a warning, but missing 4 days could carry a tougher punishment. He should find someone he trusts that can tell him the exact actions that could be taken against him.