Questioning the ethics of using this technology for Deer hunting is exactly on topic, according to the original post. The question was asked, "Is it ethical?". So it's open season on that question. Even if legal, I have reservations about it.
On one hand there is the concept of legal versus illegal. This is society's constraint upon what it deems as wrong or bad. It doesn't take much examination to see that the law is an imperfect tool.....
On the other hand there is a more ancient concept of right versus wrong or good versus evil, which probably led to laws by the time societies became larger than simple clans...
Just because something is legal doesn't make it good. The law is supposed to be a tool for good, but it's an inadequate substitute for a functioning conscience.
And then there's such a thing as situational ethics, like a massive overpopulation in a deer herd such that they become much more of a Varmint than a game animal... I haven't seen it but I don't doubt that some regions have.
So then, ethics go beyond mere law.
If the law is your only measure of right and wrong, then ethics is an alien word, devoid of meaning. So we end up with more laws since people will not constrain themselves without enforcement.