We have the technology to "grow" human-compatible organs by deleting genes from pig or sheep embryos and inserting human stem cells that will hopefully replace the missing genes that code for kidneys, liver, heart, whatever.
The problem is that what if that human DNA gets incorporated into ALL the embryo without killing it? You might end up with a pig with exceptionally high intelligence, or with human-like facial features.
Would it be ethical to then kill that pig to harvest its liver for some alcoholic who ruined his own?
I don't have the answer to that question. All I know is that I love that science is decades ahead of the laws that are supposed to govern it. And I know that if we can make a smart pig with a human face.....it must be done. That would be so awesome.