AFAIK in France you can ask the doctors to stop trying to revive you, but not to actively kill you. But the law changes quite frequently so I'm not very sure of that.
Edit : I was also told that it's not very uncommon for doctors to "overdose" terminal ill patients (especially those with terminal cancer) with morphine or other opiate derivative - they give a dose high enough to stop pain, even if it can lead to death. But I'm not sure how legal it is, nor exactly how common.
I'm reposting this from HN's front page, because it brought up a non-cached thought on cryonics:
In short, end-of-life medical care is often pointless, painful and costly; doctors and ER personnel know this so well that they go to great lengths to ensure it doesn't happen to them.
It seems as if our systems and conventions around end of life are designed to not let people have a say in how they spend their final moments, even when letting them have their way would result in significant savings (note the dollar figures quoted above). I've already speculated on why that might be, but I keep seeing that turn up in unexpected ways.
I suspect that this is the bigger obstacle to cryonics, not so much e.g. the lack of scientific proof. "Freeze me cheaply instead of spending insane amounts of money on brutal attempts at keeping me alive" sounds like a sensible thing to tattoo on your chest, but the evidence suggests that it wouldn't be honored any more than "DNR" tattoos.