There are no "inalienable rights" that come from birth in the Buddha's teaching as far as I know. I believe that that concept is not supported. Are you saying that a baby has the "right" to own a gun? How about a tank? What does lead on from birth is death.
You are right. The concept of human rights does not exist in the Dhamma. Plenty of modern concepts do not come directly from the suttas, such as gay marriage or adoption, but they can be supported on Buddhist principles and are not inherently against the Dhamma. The Buddha taught some basic morality for householders, so we can avoid the worst kamma or situations that lead to it, as well as concepts such as the 4 immeasurables. As Buddhists living in 2020 we can then use these basic moral principles and meta-concepts to inform our politics, should we wish to be politically active or to express an opinion on political matters. Of course as people's perceptions, experiences and understanding differ there will be different conclusions reached by Buddhists regarding worldly matters and politics despite us sharing the same religion and intentions. For me, when it comes to worldly matters and politics human rights are the best way to navigate the world whilst staying true to Buddhist principles. I see nothing in human rights which goes against the Dhamma and plenty of ways that they are compatible with the Dhamma. As I have then adopted the view of human rights it follows that I see these rights as being inalienable. Part of that worldview is that all people have a right to self defense and to bear arms.
Babies and children have human rights. When they come of age they can then own a gun, if the state recognises said right. Until they are an adult they are under the protection of their mother and father, or guardian. In the US I believe you can own a tank, if you can afford it.
Rights come from society and shared values. International human rights violations come about when international laws and international values are ignored.
They came from the minds of philosophers and were not widely supported when initially thought of by society at large. Rights and the concept of liberty were also met with violent opposition and still today authoritarians and totalitarians of every stripe despise the concept. In the west the most vocal opposition now comes from "Progressives". Rights then existed before society and the state accepted them. You can of course believe that humans only have human rights when the law states that they do. Its not a position I would fill, but you can take that place if you wish. That would mean, however, that countries like North Korea are not violating the human rights of their population. Falling back on international law doesn't help much either. To give an example, Saudi Arabia and other Islamic countries refused to sign up to the UN Deceleration of Human Rights. By your logic, they were then not violating the rights of their citizens as they were not bound by international law nor did any state law acknowledge said rights. By my logic, they were violating rights. Also by your logic, if a country pulls out of international treaties regarding rights and then abolishes rights legislation in their country then they are not violating any rights, since the laws do not exist or apply. By my logic, they are. My position then is that rights are a deontological moral principle that are required for there to be the free and fair society. A society that is closest in line with the Dhamma. The law then can either acknowledge or ignore someone's rights, but they can never take them away. They can only ever violate them, or not.
Rights then to me are a moral principle and a legal one. It seems for you they are only legal concepts.