The teacher, Matthew Hirschfelder, was charged with first-degree sexual misconduct with a minor for allegedly having sex with a Hoquiam High School senior in 2006. He challenged a judge's refusal to dismiss his case, arguing the student wasn't a minor because she was 18.

Hirschfelder, who was 33 at the time, also denies any sexual relationship occurred.

A three-judge panel of the Washington Court of Appeals unanimously agreed that the case should be dismissed. While the law was written vaguely, a review of legislative history shows that lawmakers only intended to criminalize contact between teachers and 16- or 17-year-old students — not those over 18, the court said.

"The name of the statute is 'sexual misconduct with a minor,'" said Hirschfelder's attorney, Rob Hill, stressing that the state recognizes that an 18-year-old is no longer a minor.

The state's code of professional conduct for teachers still prohibits any sexual advance toward or contact with pupils, whatever their age, and teachers can be fired for it. Sexual contact with students younger than 16 is considered child rape or molestation; the age of consent in Washington is 16.

Hirschfelder has not been able to work as a teacher since late 2006, when he was placed on administrative leave pending an investigation by the school board. He was arrested and charged in spring 2007, after a former choir student told police she had a monthslong affair with him that began shortly before she graduated.

His case did not go to trial because it was stayed pending the appeals court ruling, Hill said. He has been tuning pianos to make ends meet.