There's a great summary at Why Evolution is True of the current legal and ethical state of affairs in the U.S. for physician-assisted suicide, inspired by a current New York Times piece. It helps to recall the recent piece showing that show in terminal illness, physicians choose less-aggressive life-preserving measures for themselves than non-physicians. I wonder what that means?
Of note, the main subject in the NYT piece is a doc with ALS (Lou Gehrig's), a nightmare disease by any measure.
Much if not most of the resistance to legal euthanasia for humans is driven by religion. Here is a very, very clear case where religion makes people suffer more.