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 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. Overall, it appears the Ministry of Magic generally limits enforcement of the decree to situations where underage wizards perform magic in front of Muggles.
Paragraph C of the clause 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 using the spell, or the lives of other witches, wizards and Muggles are threatened.
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. Also, if an underage student unintentionally performed magic out of emotional stress, the Ministry may consider this to be accidental magic, and not punish said student, as Dumbledore noted that even the best of adult wizards cannot always control their emotions, and Fudge did somewhat take this into account when he spoke to Harry about it.
The use of objects already enchanted by someone else does not count as a violation, as stated by Ronald Weasley, at that time aged 12, when he and his brothers Fred and George, aged 14, used their father's flying Ford Anglia during the summer holidays.
- Ron Weasley: "We can fly the car to Hogwarts!"
- Harry Potter: "But I thought –"
- Ron Weasley: "‘We’re stuck, right? And we’ve got to get to school, haven’t we? And even underage wizards are allowed to use magic if it’s a real emergency, section nineteen or something of the Restriction of Thingy ...’"
- — Harry Potter and Ron Weasley while stuck at the barrier to Platform 9¾[src]
|Lily Evans||Magic||Between 1971 and early January 1977||Received a few warning letters||None of her warning letters were “too serious”.|
|Hermione Granger||"A few simple spells"||Summer of 1991||No action taken||Hermione told Harry Potter and Ron Weasley just prior to their first year at Hogwarts that she had successfully cast a few spells, but apparently, she received no notice or warning about this being banned.|
|Harry Potter||Illegal use of a Hover Charm||31st July 1992||Official warning||The Hover Charm was actually produced by the House-elf Dobby.|
|Harry Potter||Illegal use of the Inflating Charm on Marjorie Dursley||August 6th 1993||No action taken||Action not taken due to the recent escape of Sirius Black from Azkaban, and the need to keep Harry safe. Additionally, this was considered "accidental magic".|
|Harry Potter||Illegal use of the Patronus Charm in front of a Muggle||2 August, 1995||Expulsion from Hogwarts, later rescinded and given a hearing||Acquitted of all charges due to the fact that he technically did not break any laws. Dolores Umbridge was the one who secretly orchestrated this incident as part of the smear campaign against Harry.|
- Harry Potter performed the Wand-Lighting Charm shortly after his illegal usage of the Patronus Charm and letter, it did not add to his offence.
- Tom Riddle, at age 16 during his summer vacation, used the Stunning Spell to incapacitate his maternal uncle, and then took his wand for multitude of uses: the Unlocking Charm to break into the Riddle House, the Killing Curse to murder his paternal family, and then to implant a false memory into his uncle to frame him. The Ministry never even took Tom into account for the multiple breaches, let alone the crimes, as his uncle was in the vicinity, who instead became the suspect for every piece of magic performed.
- Bellatrix Lestrange trained her nephew Draco Malfoy in various fields of magic, which would most likely require Draco himself to use magic, during his summer vacation at age 16. Due to Draco being raised in a magical household, with both his mother and aunt being adult witches (albeit the latter being a wanted criminal), Draco's breaches could not be detected.
- When Harry Potter was caught in the Battle of the Seven Potters, he used several spells to retaliate against the Death Eaters, such as the Disarming and Mending Charms. The Ministry ignored this breach due to wanting to keep the Azkaban breakout a secret. However, this may be because the Ministry was currently assisting Harry Potter, and recognised that they were in a life-threatening situation, as well as the fact that the Ministry was not completely under Voldemort's regime at the time.
- Before Sirius Black defected from his family at age 16, he used the Permanent Sticking Charm to stick some muggle pictures of girls in his room. His breach was not detected due to his household being a magical family.
Behind the scenes
- In the film adaptation of Harry Potter and the Chamber of Secrets, it is Hermione Granger who magically repairs Harry's glasses at Diagon Alley, not Arthur Weasley, which should be a violation of this decree. However, because the only Muggles around were those aware of the Magical community and she was accompanied by parents, Hermione was not punished.
- In the film adaptation 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 in 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; moreover, it was not performed in front of Muggles.
- In the film adaptation of Harry Potter and the Order of the Phoenix, Umbridge's involvement in the Dementor attack on Harry Potter and Dudley Dursley was omitted. As a result, the one behind the attack was never identified in the film.
- In the film adaptation of Harry Potter and the Order of the Phoenix, when Dumbledore brought up Clause 7 as a justifiable defence for Harry's breach of the decree, Cornelius Fudge immediately and directly countered that "laws can be changed if necessary", suggesting that he intended to make it illegal for underage wizards and witches to use magic at all, even if was to save lives.
- It's unknown how magic is restricted for those wizards who are home-schooled. It is possible that they are only allowed to use magic at their home, or only when their private teacher is present. Albus Dumbledore also allowed Harry Potter to perform magic in summer 1996 when he accompanied him to find Horace Slughorn.
- Harry Potter and the Chamber of Secrets (First appearance)
- Harry Potter and the Chamber of Secrets (film) (Mentioned only)
- Harry Potter and the Prisoner of Azkaban (Mentioned only)
- Harry Potter and the Prisoner of Azkaban (film) (Mentioned only)
- Harry Potter and the Order of the Phoenix
- Harry Potter and the Order of the Phoenix (film)
- The Tales of Beedle the Bard (explained by Albus Dumbledore in a footnote)