Capital punishment in the United States:

Other states with long histories of no death penalty include Wisconsin (the only state with only one execution), Rhode Island (although later reintroduced, it was unused and abolished again), Maine, North Dakota, Minnesota, West Virginia, Iowa, and Vermont. The District of Columbia has also abolished the death penalty; it was last used in 1957. Oregon abolished the death penalty through an overwhelming majority in a 1964 public referendum but reinstated it in a 1984 joint death penalty/life imprisonment referendum by an even higher margin after a similar 1978 referendum succeeded but was not implemented due to judicial rulings.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". In what year did an Oregon referendum succeed in restoring the death penalty, only to be passed due to a court ruling?
unanswerable