The indeterminate sentence review board is hereby granted authority to parole any person sentenced to the custody of the department of corrections, under a mandatory life sentence for a crime committed before July 1, 1984, except those persons sentenced to life without the possibility of parole. No such person shall be granted parole unless the person has been continuously confined therein for a period of twenty consecutive years less earned good time: PROVIDED, That no such person shall be released under parole who is subject to civil commitment as a sexually violent predator under chapter
71.09 RCW.