OK, not a bad answer but two things.
First, you're a libertarian when it comes to the human body, but not when it comes to personal property. Acknowledged. HOWEVER.... note that not everybody shares that view. Plenty of people are libertarian when it comes to body AND property, while others are not libertarian in either case (myself).
In actual fact, (second point) it's not legal to sell your kidney on ebay in the USA and it has little to do with trade regulations. It's the same reason it's not legal for me to go ask a doctor to end my life if I'm feeling depressed. It's the same reason it's not legal for me to have a doctor cut off my healthy leg just for fun.
We as a society in the US are not libertarian when it comes to the body. If you are, just understand that not everyone thinks the same way.
I noticed that you are Dutch - I believe things like euthanasia are legal in the Netherlands, so that libertarian attitude is more prevalent over there than in the United States.
But I am not a libertarian. I am progressive/social democrat and what happens to someones property, as long as it is done in accordance with the law of the land and protected by an independent and fair judiciary, can be legal even if it is not fair. But your property is not the same thing as your body IMHO, you have a much higher right of ownership over your body than over the things your possess.
That doctors are not allowed to do harm (and removing a kidney can be seen as doing your body harm) and that is a legal and ethical requirement. By removing an egg, zygote, embryo or even early stage fetus, you are not harming your body IMHO. As for removing your leg, if it is done for psychological reasons, then I think removing your healthy leg can be allowed. I have seen documentaries about people with body dismorphia who have real mental suffering and anguish because they are mentally convinced that (for example) they are supposed to be without a left lower leg/foot. These people at times risk their lives to disfigure their bodies in such a way that it conforms with their ideal picture. But these cases are rare and should only be done after long and intensive mental treatment to try and "heal" their condition. But if that is impossible, and the only way to stop them from risking their lives is by amputating a foot or leg, than maybe that should be possible.
Legal is a big word when it comes to euthanasia. If you follow the rules and regulations to the letter, you will not be prosecuted. Break those guidelines and you are open to prosecution.
The same with cannabis, people act like in the Netherlands you are allowed to smoke to your hearts content. That is not the case, if you smoke cannabis in a coffee shop you will not be prosecuted. Take your legally bought cannabis/pot home with you and you are stopped by the police, you will be relieved of that cannabis by the police because it is not legal to be in possession of said cannabis outside the coffee shop. Carrying anything up to 5 grams will not be prosecuted but as it is still illegal, your drugs will be impounded and destroyed.
The odds of you being nicked with 3 grams of pot on you are slim but if you drive impaired or do something else that puts you on the radar of the police, you will be searched and upon finding cannabis this will still be impounded because even though it is decriminalized, it remains illegal to own cannabis. Anything above the 5 grams will most likely get you prosecuted though. We do not want to be an interfering nanny state but not prosecuting possession of cannabis/pot is not the same as it being legal.
I think the Netherlands is the perfect mix (if you want to call it that) of libertarians, liberals, progressives and social democrats/socialists when it comes to social issues like drugs possession, euthanasia and abortion. But also when it comes to, for example support of religious education. In the Netherlands religious education has the same right to public funding as non-religious education.
I am an atheist so my parents let me go to a public school from ages 6 to 12. Then, because we lived in a very Christian region of my country, my parents were not able to find a public secondary school for me but there were a lot of choices still left. I went to a progressive protestant school next where I had to go to religious studies (mandatory) but mostly it was more civil classes with religion mixed into it. Next I went to a catholic higher education but there I was allowed to skip religious studies because there it was not mandatory. But all of these schools, the religious and public ones still had the same public funding because they all had to comply with the countrywide study targets and methods. Every kid had to do the state run exams in the end and the books schools had to use also had to be to certain mandatory standards and content.
What I am really saying is that we are a weird and somewhat messed up country. The country is mainly steeped in Calvinism, with large blocks of Catholicism and large blocks of the country where social democracy reigns supreme. We have always been a country of compromise due to our diverse make up and political reality. To be honest, we are a bit nuts and that is what works here in the Netherlands but is not easily copied to other countries (nor should it be).
We like that people who are dying a horrific death have the freedom to choose to end their own lives (as long as the rules are followed) but doctors still have the right to not want to participate in euthanasia. Every doctor has the freedom to choose whether or not they want to perform the medical procedure that is euthanasia.
But what is imperative here is that we would not let an animal suffer a horrendously painful death, than who are we to deny someone who is fully capable to make an informed decision, a humane end to their life if they should choose to.
My grandfather died through euthanasia when it was not regulated in the Netherlands. The doctors over-medicated him with morphine. He was in the final stages of lung cancer. A disease that was made worse with his miners lungs. He had worked most of his adult life in the dutch coal mines and his lungs were shot before he was 50. When he contracted lung cancer he quickly deteriorated and the strong willed and independent man that he had been all of his life was so weak that slime was pooling in his lungs and the nurses had to palpitate his chest so that he was not suffocating too badly from it. He was so weak that he was unable to cough anymore. His legs had diminished to where his upper legs were smaller in diameter than my wrist. He was barely able to sit let alone stand anymore and he was weakening daily. His greatest fear was that he was going to suffocate to death. In the end, on his own request, he was given a larger than normal dose of painkilling morphine. His body was unable to handle that larger dose and he died peacefully in his sleep. He died after having said his goodbye's and with what pride he had left in him. We were all sad to have lost him, but all of us were happy that his suffering had ended.
Now, like him, everybody in the country has the right to decide to die when they are dying and they feel it is time. Most will wait until the last moment and even more will never choose euthanasia. But if they wanted to, they had the choice to make that decision.