They didn't. The law allowed terminally ill people to request lethal doses of drugs so they could end their own lives. What the court allowed is the state's power to govern itself.
Because Ruth Bader Ginsberg and John Paul Stevens are such states right advocates.
In other words they allow people to kill themselves with controlled substances. Does this mean that someone wanting to kill themselves can get around federal gun laws, if a gun and not an injection is the method of choice.