In a 7-2 ruling on Thursday, the high court dismissed a petition by Jonathan Gentry, who argued that the move unlawfully changed the terms of his sentence.
The majority says that housing in the special unit is a privilege that can end for a number of reasons, including budget cuts.
The dissenting justices argue the petition should be heard in superior court to answer questions, including why prisoner benefits, including visits with family, had to end with the closure of special housing.
Gentry was sentenced to death in 1991 for killing a 12-year-old girl in Kitsap County.
