You mean like the laws we have today against committing murder, or against owning a firearm if you are a convicted felon? It is not enough to posit a law. One must also consider the likelihood of that law being followed by one and all. We see with ALL laws we pass in our society today, it is not just a matter of one or two people disobeying important laws. LARGE numbers of people will disobey a law, especially if they see a benefit to themselves. It does not even have to be a large benefit to themselves to break a law of today's technology. Now consider just how huge a benefit time traveling would be, and then estimate accordingly how many people you think will obey these laws. And in time travel, it only takes a few people not obeying such laws for people throughout time to become aware that time travel is a reality. Darby's point stands, completely notwithstanding any consideration you may give for any man-made (and man-enforced, if possible) laws for time traveling.
RMT