Decree for the Reasonable Restriction of Underage Sorcery

The Decree for the Reasonable Restriction of Underage Sorcery, established in 1875, is a key piece of wizarding law enforced by the Ministry of Magic. Commonly referred to as the law against underage magic, it prohibits young witches and wizards who have not yet come of age (seventeen years old) from performing magic outside of their school. The primary purpose of the Decree is to prevent untrained magic-users from accidentally exposing the magical world to Muggles and to protect the young individuals themselves from magical mishaps. Enforcement is handled by the Improper Use of Magic Office and is primarily monitored through a magical signature known as the Trace.

The Trace is a magical charm placed upon all young witches and wizards. It functions as a detection system for the Ministry of Magic, alerting them whenever a spell is cast in the vicinity of an underage magic-user. However, the Trace has a significant limitation: it can only detect that magic has been performed near the individual; it cannot identify the specific caster. This limitation leads to several practical outcomes:

• False Positives: An underage wizard can be blamed for magic performed by another being in their presence. For example, Harry Potter received a warning letter when the house-elf Dobby performed a Hover Charm at Number Four, Privet Drive.
• Leniency in Wizarding Households: The Ministry of Magic does not typically follow up on magical activity detected in known wizarding homes, as it is impossible to determine if the magic was performed by an adult or a child. This is why the Weasley children were not constantly reprimanded for using magic at The Burrow.
• Automatic Cessation: The Trace breaks automatically and permanently the moment a witch or wizard turns seventeen. This event was of critical importance for Harry Potter, as Lord Voldemort and his Death Eaters used the breaking of his Trace to pinpoint his location and launch an attack.

The Improper Use of Magic Office is responsible for enforcing the Decree. When the Trace is triggered in a Muggle-inhabited area, the office sends a warning to the underage individual. The severity of the penalty depends on the nature of the offense and the individual's prior record.

• First Offense: Typically results in an official warning letter sent by owl post.
• Further or Serious Offenses: Can lead to a formal disciplinary hearing before the full Wizengamot.
• Maximum Penalty: For severe or repeated violations, the consequences can include expulsion from Hogwarts School of Witchcraft and Wizardry and the snapping of the offender's wand, effectively barring them from practicing legal magic.

While the Decree is strict, there are several known exceptions and loopholes:

• Life-Threatening Situations: Clause Seven of the Decree permits the use of underage magic in “exceptional circumstances,” specifically in situations of life-or-death peril to the caster or others. Harry Potter successfully used this clause as his defense when he faced the Wizengamot for casting a Patronus Charm to fend off Dementors.
• Within Hogwarts: Students are permitted and expected to use magic within the grounds of Hogwarts, as it is a controlled and supervised magical environment. The Trace does not seem to trigger official warnings for magic performed at school.
• Ministerial Discretion: The Minister for Magic holds the power to pardon violations. Cornelius Fudge chose to dismiss Harry Potter's illegal inflation of his aunt, Marge Dursley, because he was more concerned with Harry's safety following the escape of Sirius Black.

• Harry Potter:
  1. 1992: Falsely accused of performing a Hover Charm cast by Dobby. He received an official warning.
  2. 1993: Unintentionally used magic to inflate Marge Dursley. Cornelius Fudge pardoned this offense.
  3. 1995: Cast a Patronus Charm to save himself and Dudley Dursley from two Dementors. He was formally charged but cleared of all charges by the Wizengamot.
• Tom Riddle: As a teenager, Tom Riddle murdered his Muggle father and grandparents. He used his uncle Morfin Gaunt's wand, and because the Trace detected magic in a known wizarding residence, the Ministry of Magic wrongly convicted Morfin for the crimes.

• In the film adaptation of Harry Potter and the Prisoner of Azkaban, Harry is shown practicing the Lumos charm under his bedcovers at the start of the summer holiday. This is a direct contradiction of the book's strict rules, as using any spell at the Dursleys' home would have immediately triggered a warning from the Ministry. (film)