I suspect natural law is to be taken in its philosophical manner, which means the fundamental laws that man would live by of his own volition. There's been many philosophers debating on what natural law is and means to people, notably by luminaries such as Fuller et al. For example, where one's laws conflict with human nature, which is to be obeyed? This discussion inevitably ends up in Nazism. The idea was that Human Rights legislation would enshrine such natural law, but I see that as a flawed concept. Is natural law contrary to murder? If so, what about in times of war? I fail to see a great difference between how one is killed. My point is that natural law is far from a definite term. Few would argue in favour of paedophilia, but it takes all-sorts...
However, I specialise in IP and didn't pay great attention to lectures in the law of real property, so this is as far as my answer goes. It seems as though natural law would not likely concern itself with this (Taking into account the HRA). But seriously, I remember a question strikingly similar to this a while back- in the time it's taken for you to wait and repost, you could have read up on this yourself.