A 17-year-old boy was convicted of child pornography charges after sending an unsolicited picture of his penis to a 22-year-old woman.
Eric Gray was sentenced to 30 days' confinement in a highly unusual case in which he was classed as both the offender and an exploited minor.
Senior judges upheld Gray's conviction despite an appeal from his legal team, who had argued the law was ambiguous and infringed upon his constitutional rights.
Washington Supreme Court heard the teenager sent a photo of his erect penis to the woman in a text message in 2013.
He sent a second text reading: "Do u like it babe? It's for you."
The woman reported the messages to the police and said she had also been harassed by anonymous calls, which she suspected were from Gray, over the previous year.
Gray, who has Asperger’s syndrome and was already a registered sex offender from a previous incident, eventually admitted sending the texts.
A juvenile court found him guilty of disseminating images of a minor engaged in sexual conduct.
His lawyers challenged the conviction and argued the law should not be applicable to minors willingly sending photos of themselves.
But the supreme court rejected their appeal, ruling the conviction should be upheld because Gray was "not a minor sending sexually explicit images to another consenting minor".
"[The law] prohibits developing or disseminating sexually explicit images of minors," the judgement read.
"On its face, this prohibition extends to any person who disseminates an image of any minor, even if the minor is disseminating a self-produced image. Because the statute is unambiguous, we take it on its face and find that Gray's actions are included under the statute."
The eight judges made the ruling seven to one.
The dissenting judge, Justice Sheryl Gordon McCloud, described the ruling as an "absurdity".
She argued child pornography laws were intended to protect any minor depicted in an explicit photo.
"The majority, however, holds that the statute takes the punitive approach to the depicted, vulnerable victim child," she wrote.
"I can't believe the legislature intended that absurdity."
