Law of Physic is not that absolute in the first place such as in place like event horizon. Assuming there is one, time travel does not use law of physic in the first place. It may use another set of law that is very obscure to us in current time, the Law of Time. Assuming there is Law of time in the first place, we need to know what aspect in this law are readily available to be manipulated , assuming again if it can be manipulated in the first place. What if , the law of time is an absolute?