The Supreme Court of Appeal in Rome on Wednesday overturned a rape conviction, saying that the supposed victim must have agreed to sex because her jeans could not have been removed without her consent.
A court in the southern town of Potenza had convicted a driving instructor of raping his 18-year-old pupil.
The instructor, aged 45 and identified only as Carmine, had been sentenced to 34 months' jail.
His defence had argued that the young woman - identified as Rosa - had consented to sex, a version of events which the woman strongly denied.
The Supreme Court ruled that it was impossible to remove a pair of jeans "without the collaboration of the person wearing them", and that the young woman must therefore have consented to sex.
In a judgement likely to anger women's rights organisations, the rape conviction was reversed.
Driving instructors in Italy have a reputation, deserved or undeserved, for molesting young female pupils, and the case appeared at first to be a familiar story of sexual assault on a lonely country road.
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