The Supreme Court has ruled that a father who took his daughter out of school for a holiday to Disney World in term-time acted unlawfully.
Isle of Wight Council appealed against an earlier court judgment that said Jon Platt had acted lawfully when he took his child to the USA for two weeks.
The Supreme Court allowed the Isle of Wight's appeal, meaning Mr Platt will be required to pay a fine or face jail time.
The case has implications for any parent in Wales, England and Northern Ireland who takes their youngster on holiday within term time without permission of the headteacher.
Mr Platt had successfully argued at the High Court that he was justified in taking his daughter to Florida because she had a good attendance record during the rest of the year.
But Lady Hale, deputy president of the Supreme Court, said: "Unauthorised absences have a disruptive effect; not only on the individual child but also on the work of other pupils.
"If one pupil can be taken out, whenever it suits the parent, so can others.
"Any educational system expects people to keep to the rules. Not to do so is unfair to those obedient parents who do keep to the rules.
"It follows that the appeal must be allowed."
Mr Platt's initial appeal was based upon the government legislation that underpins the ability of an LEA to fine parents for unauthorised absence, which said they must ensure children have "regular attendance".
His daughter had more than 90% attendance during the school year - the threshold contained in the Isle of Wight policy on regular attendance.
The Supreme Court took the view that the meaning of "regular" was "in accordance with the school's attendance rules".
As a result of legislation passed in 2013, pupils at all state schools in England must attend unless they are granted a leave of absence - something Mr Platt was not granted in this case.
Parents in Northern Ireland and Wales also face prosecution if they do not ensure their child attends regularly.
Mr Platt said on the steps of the Supreme Court after the judgment: "The Supreme Court has just reversed decades of judicial precedent.
"They didn't just say that the High Court judge who heard my case... misinterpreted the law, they have concluded that the earlier High Court decision from 2006 and one from 1969 were also wrong in their interpretation of the law.
"Be in no doubt, despite the judgment, I followed the law precisely laid down and interpreted by High Court judges in two separate cases. They told me that to attend 'regularly' was to attend very frequently.
"So I decided not to pay a £60 penalty notice because my daughter had otherwise perfect attendance at school.
"With this judgment those precedents have been swept away and the consequences can only be described as shocking.
"(Regularly) now means to attend on all the days and at all the times that a school requires it. Every unauthorised absence, including being a minute late to school, is now a criminal offence."