～ておる means the same as saying ～ている, so in the example above 禁じられております means "～is forbidden." The difference is the level of politeness. ておる is a way of expressing modesty to people of higher rank or status or to people for whom you are providing a service. This is part of what is known as 謙譲語 (けんじょうご); one of three types of polite language used in Japanese. I hope this helps. If you have further questions, let me know.