Decree for the Reasonable Restriction of Underage Sorcery

"Dear Mr. Potter, We have received intelligence that you performed the Patronus Charm at twenty-three minutes past nine this evening in a Muggle-inhabited area and in the presence of a Muggle."

- Mafalda Hopkirk's letter adressed to Harry Potter on 2 August, 1995.

The Decree for the Reasonable Restriction of Underage Sorcery is a bylaw of the Ministry of Magic, written in 1875, which bans the use of underage magic outside of school. The Decree is enforced by the Improper Use of Magic Office in the Ministry of Magic. The restriction is for wizards and witches who are under the age of seventeen, upon which The Trace still operates. Even so, the Ministry does recognise that they may have to use magic in certain situations such as self-defence in a life-threatening situation. In addition, young children of below school age, or children who are not in possession of a wand, are mostly exempt from the rule since they usually have little or no control over the magic they perform.

Known contents
"In the matter of Harry Potter, the law clearly states that magic can be used before Muggles in life-threatening situations."

- Albus Dumbledore at Harry Potter's hearing

Paragraph C of the cause states that it is a crime to knowingly perform magic in a Muggle-inhabited area and in the presence of a Muggle. However, Clause 7 also states that magic can be used in front of Muggles in exceptional circumstances, including situations when the life of the witch or wizard is threatened, or the lives of other witches, wizards and Muggles are threatened.

Also, it seems that a high-authority person may give permission for an underage student to perform magic under circumstances; as Hogwarts Headmaster, Albus Dumbledore gave Harry Potter such an instruction if an attack was to eventuate, when he was 16 years old.

Behind the scenes

 * In the film version of Harry Potter and the Philosopher's Stone on the Hogwarts Express, Hermione casts the Oculus Reparo spell to fix Harry's glasses - and she does it again in public in Diagon Alley in the film version of Harry Potter and the Chamber of Secrets. There is no indication that she got into trouble for either non-school use, as it wasn't performed in a Muggle-inhabited area, or in the presence of a Muggle. It is also possible the Reparo spell was considered too mundane or harmless to violate the so-called "Reasonable Restriction." And the first use of the spell might have been ignored if the train is considered an extension of the school. This latter point is supported by Harry Potter and the Order of the Phoenix in which Ginny Weasley casts the Scouring Charm aboard the Express without penalty. The second may have been ignored as she was in Diagon Alley which is a part of the wizarding world, and the only Muggles present were her parents and possibly the parents of other muggle-borns who were already aware of the existence of the wizarding world.
 * In the film version of Harry Potter and the Chamber of Secrets Harry did not receive a warning for the illegal use of a Hover Charm which caused a continuity error with the following films due to the fact that the book version caused the Dursley family to learn that Harry cannot use magic outside of school.
 * The film version of Harry Potter and the Prisoner of Azkaban has Harry using the spell Lumos Maxima and yet receiving no warning. It is also possible Lumos Maxima was considered too mundane to be monitored.
 * In Harry Potter and the Order of the Phoenix, during Harry's hearing, even though Harry had been given an official warning in 1992, and that he had not punished Harry personally in 1993, Cornelius Fudge attempted to use these incidents to expel Harry from Hogwarts despite those incidents being completely irreverent to his recent illegal use of magic. In addition, despite Dobby being a witness in the underage magic incident in 1992, Fudge refused to let him testify due to Dobby being a House-elf.

Appearances

 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * The Tales of Beedle the Bard