Who decides rights?

In 1948 the UN General Assembly adopted The Universal Declaration of Human Rights. In it there is a montage of the expected and the unexpected. Everyone expects "equal in dignity", "right to life", or even "the right to a nationality". Not everyone is on board with "Everyone has the right to take part in the government of his country" or " the right to a standard of living adequate for the health and well-being of himself and of his family". And there is a surprising one--"Everyone has duties to the community"--listed among the "rights". I'm not offering this as an argument for or against any of these. My question is much more basic. My question is this: Who decides what rights we have?

There are a variety of components here. First, we need to distinguish between a right and a privilege. A right is something owed you. It is a just claim. A privilege is a grant given under certain conditions to certain persons or groups. It is an advantage given that was not owed. I'm not asking about privileges; I'm asking about rights. Second, there are different kinds of rights. There are natural rights and there are legal rights. Obviously legal rights are entitlements bestowed by the law. Your right to vote, for instance, isn't something you're born with. It is bestowed by law. (For instance, a person born in a country that is not a democracy or republic will not have a legal right to vote.) Natural rights, then, are rights bestowed by "nature", be it human nature, natural logic, or by divine edict. The right not to be murdered is stated by God in Genesis when He says, "Whoever sheds man's blood, by man his blood shall be shed, for in the image of God He made man." (Gen 9:6) That is, "made in the image of God" gives all image bearers (humans) a right to life. The law doesn't confer that right. This line of rights is recognized in the Declaration of Independence. "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable rights." The Bill of Rights was not conferring rights, but defending them.

But now we run into problems. As growing numbers of loud people argue there is no Creator or, if there is, He isn't of particular concern, the supposed source of "unalienable rights" is eliminated. Conversely, more and more people are seizing more and more rights. Women now claim "Reproductive Rights" which men don't have. Young people claim a right to a college education--free. There is some sort of "right" that allows the homosexual community to redefine marriage and call it "marriage equity", a right tacked onto a whole series of rights afforded to a group that wasn't before. Use the synonym, "entitlement", and you'll certainly come up with a host of new "rights" that no one thought of before. And I want to know, given the absence of a Creator, by what authority rights, whether old or new, are determined?

It seems as if they're simply determined based, perhaps loosely, on that whole "life, liberty, and pursuit of happiness" thing. So I have a right to whatever makes me happy. But, look, a new Tesla would make me happy and no one seems to be buying my claim that it's my right, so that can't be it. And haven't we already determined that any lame "Creator"-based logic is wrong? So don't we have to nullify at least that portion of the Declaration of Independence and its ramifications? I mean, we removed the "right to life" back in 1973 with Roe v Wade, so that's not settled, is it? It seems to me that rights are shifting and accumulating and no one is batting an eye. It seems to me that they're accumulating out of thin air. Who's manning the "rights" machine?