“Nature” itself does not seem to grant any rights – especially if we perceive human nature as the end result of evolution, progress through the hunter-gatherer stage, competition between primitive societies, etc. What seems to result from evolutionary theory is only the right of the stronger – but not the right of survival, even for the strongest, since a multitude of the weak may defeat the efforts of the stronger. It’s a very precarious situation, perhaps best described by Thomas Hobbes as the “war of all against all.”
It would be an understatement to say that natural-law theory assumes a loftier view of human nature. And if we believe that there is such a thing as a natural law governing all humans, and optimally providing guidance to civil laws, natural rights seem to be necessarily entailed in the very idea of natural law. For example, following the natural-law theory of St. Thomas Aquinas, which divides up into three “precepts,” we find inevitable implications of natural rights:
1) The precept of self-preservation obviously implies the right to preserve one’s life, to maintain one’s health, to work according to one’s ability to support oneself, and to have sufficient property to survive and progress normally in the pursuits of life. And since all humans have this right, it follows that we all have a duty to respect that right in others, and not intentionally impede it, except in cases of self-defense or defense of others.2) The precept of propagating the human race and care for progeny, also implies the right to have children (not “reproductive rights” in contemporary new-speak), and to nurture and care for their health and education. Concomitant with this is the duty to respect this right in others – not to impede it (as for example, by past policies of forced sterilization in California and other states, and the Chinese one-child policy).3) The third, and most important precept, for rational beings, is the duty to search for the truth, to learn and become educated according to one’s ability and status in life. Corresponding to this duty is the right to have access to whatever instruments and facilities are necessary for learning; as well as the duty not to prevent others from searching for the truth, nor to propagate ideologies and nostrums as a substitute for the truth. On the practical level, the duty to do what is within one’s power to support a rational, orderly social and political environment implies the corresponding right to participate in communal or political enterprises, as well as the duty not to impede others from being so engaged.
Aquinas  by Ardith Starostka ( ©2010) 
Aquinas did not bring out these rights explicitly, but, as Brian Tierney shows in his book, The Idea of Natural Rights , the concept of individual rights was implicit in various interpretations of Jus (“law,” “justice,” “right”) by Roman jurists long before the time of Aquinas.
However, the explicit definition of rights close to our modern sense began, according to Tierney, with the fourteenth-century canonist Johannes Andreae, who made the distinction between what is “right” because of law or custom, and the “right that belongs to a private person in some thing.”
The Jesuit scholastic, Francisco Suarez, whose theory of natural law builds on Aquinas, also explicitly brings out the notion of rights as powers possessed by individuals.
Protestant natural law theorists in the seventeenth and eighteenth centuries emphasized what Aquinas referred to as the third precept of natural law (the law of properly exercising our rational powers). Natural law, for theorists like Pufendorf, Cumberland, and Grotius, consisted in thinking and acting reasonably, in concert with others, and supporting the social/political rights connected with the implementation of this natural law.
In drafting the Universal Declaration of Human Rights, which was adopted by the U.N. General Assembly in 1948, in the aftermath of World War II, the input of neo-Thomist Jacques Maritain was immensely influential, and the thirty rights listed in the Declaration concur very much with the rights implied in Aquinas’ three precepts.
For example, the rights “to life, liberty, and security of person,” to freedom from torture, to freedom of movement, ownership of property, just wages, help in case of disability, etc. are related to the first precept; the right to marry and found families, free of external coercion, and educate children, are related to the second; and the rights to equal protection under the law, presumption of innocence until proven guilty, education, privacy, free speech, voting, etc. are related to the third.
The almost majority acceptance of the Declaration by the member nations might even qualify as a persuasive argument that these are indeed natural rights, possessed by everyone regardless of national or ethnic origin. The Declaration was adopted by a vote of forty-eight in favor, none against, and eight abstentions (the Soviet Union, Ukrainian SSR, Byelorussian SSR, People’s Federal Republic of Yugoslavia, People’s Republic of Poland, Union of South Africa, Czechoslovakia, and the Kingdom of Saudi Arabia).
Moses by Rembrandt van Rijn (1659)
The actions of some of the signatory nations since 1948, however, have belied their words of assent. South Africa’s abstention from signing can be seen as an attempt to protect its system of apartheid, which clearly violated any number of articles in the Declaration; the Saudi Arabian delegation’s abstention was prompted primarily by two of the Declaration’s articles: Article 18, which states that everyone has the right “to change his religion or belief”; and Article 16, on equal marriage rights; and the abstention of the Soviet bloc nations was certainly influenced by Article 13, which provided the right of citizens to leave their countries.
China and North Korea signed the Declaration, but ignored it. Iraq signed, but invaded Kuwait. The United States itself, because of its acceptance of capital punishment, was delinquent regarding Article 5, which prohibited cruel or inhuman forms of punishment.
One of the rights most often breached is No.18, the “right to freedom of thought, conscience and religion. . .to change one’s religion or belief. . .and manifest one’s religion or belief in teaching, practice, worship and observance.” A recent report by the Christian group Open Doors noted that “North Korea remains the world’s most restrictive nation in which to practice Christianity,” followed by Somalia, Syria, Iraq, Afghanistan, Saudi Arabia, Maldives, Pakistan, Iran, and Yemen.
The problem is that different nations have differing interpretations of what is meant by property ownership, marriage, free speech, as well as freedom of religion. And political realities continually trump the ideal of individual rights. The contest for power among nations and between factions within nations causes a constant disregard of rights that happen to impede the goals of leaders or aspiring leaders.
The Judaeo-Christian support of natural rights is based largely on the belief that humans are created in the image of God. In Genesis 9:5-7, in the aftermath of the great flood, God’s covenant with Noah states this basis rather explicitly: “For your own lifeblood. . .I will demand an accounting: from every animal I will demand it, and from man in regard to his fellow man I will demand an accounting for human life. If anyone sheds the blood of man, by man shall his blood be shed: For in the image of God has man been made.”
Certainly also the Ten Commandments not only include applications of natural law, but imply certain corresponding rights. The commandment against stealing implies a right to property; honoring parents implies a right of parents to respect and deference; the prohibition of killing implies a right to life; the prohibition of adultery implies the right to faithfulness from one’s spouse; the prohibition of lying implies that there are those who have a right to the truth.
But it has taken centuries for some implications of these rights, which seem obvious to most of us, to become explicit: Jews and Christians believed in humans as made in God’s image, but for some reason did not see the relevance of this to the absolute prohibition of slavery. Thus the development of firm and universally accepted application of rights to issues such as slavery, the necessity of free consent of both parties to marriage, freedom of religion, etc., only came later, when economic, cultural, and political developments called for renewed reflection on just what is meant by being created in the image of God, and the “human dignity” that necessarily ensues from that belief.
Grotius by Michiel Jansz. van Mierevelt (1631)
God and Natural Rights: The seventeenth-century natural law theorist, Hugo Grotius, claimed rather dramatically in his treatise on law that natural law “would somehow equally subsist even if we granted – which cannot be done without committing the most serious impiety – that God did not exist or did not care for humanity.” This statement has helped bolster a school of thought that maintains the independence of natural law from any presupposition about God as lawgiver.
This was not, however, the intention of Grotius, who was a committed Christian, but thought that natural law was something so immanent in human nature, that it could not be modified or denied without succumbing to irrationality. He thought that natural law was so evident that denying it would be comparable to denying 2 + 2 = 4.
But if natural law is a law in any unequivocal sense, it implies a Lawgiver; and if there are any concomitant rights implied by natural law, these rights have been bestowed by the Lawgiver. Evolution, fellow feeling, social customs, etc. cannot function as lawgivers. If there is no Lawgiver as the source of natural law, then, for example, the judges at the famous Nuremberg trial at the end of World War II were appealing at most to the authoritative fact of the military victory by the allies, in their condemnation of Nazi officers and officials – many of whom were arguably within their rights according to the then-prevailing German civil laws.
If there is no God, there are also no natural rights or infractions of these rights. Only the Creator of nature and natures can bestow (and ultimately offer sanctions for) natural rights.
Civil lawmakers, courts, and heads of state can often, with a stroke of the pen, grant, if they wish, unnatural rights – the right to kill children in the womb, the right to simulate marital intercourse through use of substitute organs in same-sex partners, the right to stifle free speech and free thought by ideological police.
But the Author of nature retains the final sanctions, which can trump newly invented and broadly permissive “rights” bestowed by those in power.