People make it too complicated.
Go sit in your yard, or an inarguable public place. Your needs are provided by yourself or a series of transactions which do not impact a third party. Does the third party have the right to use your life without your permission, or to end it? No. The third party also has those rights. Everyone does. Thats what makes it "natural", they are inherent. It IS a philosophy, and it is abstract.
The problem with natural rights is - generally speaking- outside of a forum such as this, it's called common sense, or possibly humanity. It's understood at its core. And when those natural rights are broken, universally, people say "What the fuck!!? You can't do that!!" Thats how deep it is. You can't murder. You can't enslave someone. You can't take their property which they've worked for, time=money=a part of their life was traded to be able to purchase that property. And nobody can do that to you, either. It doesn't matter whose countries flag flies over your head, you're still human.
And, in society, it works in the reverse. When you disregard the rights of a human for your own purposes, if you kill or enslave or steal from them, you've forfeited your rights in the law of that society. The People, as a whole (theoretically) have established laws to punish those who break those laws. If you kill, your rights are forfeited in their eyes, and they take possession of your body and prevent you from doing it again. If you steal, you're either jailed to prevent you from stealing more or you're forced to pay restitution. The other goal of the penal system is to rehabilitate the offender. This is flawed 19th century mentality, rehabilitation is bullshit. The government knows this too, and still tries to subliminally reinforce this concept by calling jails "Correctional facilities". But for the big stuff, it works. Murderers belong in jail.
Natural rights are actually the cornerstone of a fair and ideally constructed government. To exist within its parameters you give a portion of your value and take its services and protection. Obviously, most here agree the balance has tipped into an unfair advantage in favor of the government which spawns unrest among the people its supposed to protect, but that is not the argument. The argument is do the natural rights exist, and why libertarians continually point it out.
Simple, because the libertarians are politically motivated, and have properly identified Natural Rights as the cornerstone of the existence of reasonable government. Government is meant as an extension of the population. As such, it should abide by the same laws the population is expected to abide by.
The government, therefor, should not be able to do things to the citizens which the citizens cannot do among themselves. Murder, steal, prohibit different sorts of interactions and private acts. I cannot walk up to you and use force to make you stop smoking crack, I don't have those powers. But the government can. And since nobody in their right mind would give me the powers as a private citizen to enforce the governments own laws, it is more reasonable to suggest the government also should not have that power, and thus, strike the law. Only when irreparable harm to a citizen is occurring should the government have the right to act in defense of its people. Like a litmus test (A term I use rarely), would I be punished if I stopped a murder or a rape by using force against the criminal? Probably not, I might go to trial, but ultimately would be found Not Guilty of any wrongdoing. Same goes for government. They should not be able to act with impunity and use actions which if I used would be against the law. The people in those uniforms are citizens, their power is an extension of our collective will.