Decree for the Reasonable Restriction of Underage Sorcery
1875
(CS2, CS5, PA3, OP2, OP8)

violation under paragraph C knowingly, deliberately, in full awareness of illegality, to do magic in a Muggle-inhabited area and in the presence of a Muggle (OP8)

clause 7 magic may be used before Muggles in exceptional circumstances, which include situations that include the life of the wizard or witch himself, or witches, wizards, or Muggles present (OP8)

From the HP Lexicon



Hope this helps a little

So it was ok for Lily to do magic in her home away from school because her whole family was aware of her being a witch.

but I think maybe petunia exagerated, maybe lily just showed her books and her potions ingredients or something like that (or maybe she threatened petunia of changing a cup into a rat)
don't know

I think that this is better suited in A History of Magic.
May the discussion continue there.

Mobilithreadus

Moose_Starr
LL Mod

Maybe Lily gave Petunia tea in one of those nose-biting teacups?

Jo was actually asked this somewhere (sorry I looked and couldn't find it) but she said that Petunia was exaggerating. Though there probably is some truth there in my opinion.

In "Philosopher's Stone" Aunt Petunia says that Lily came back from Hogwarts with frog spawn in her pockets and turned teacups into rats. If this is true, why wasn't Lily expelled?

Aunt Petunia is exaggerating a little; you have to allow for her state of mind when she started shrieking these things. However, just like her son, Lily was not averse to testing the limits of the Statute of Secrecy, so you can safely assume she will have had a few warning letters – nothing too serious, though.

Doing magic in front of those who already know you can do magic is much less serious than levitating a pudding in front of virtual strangers, blowing up an aunt who is ignorant of magic, or doing obvious magic in a public muggle area. Thus Harry's supposed breaches would be taken more seriously than Lily showing off a few spells to her sister. Thus it is consistent that Lily would be treated more lightly.

Actually no, doing magic at all is a very serious offense.

We aren't told that. It is against the rules, but that doesn't mean that breaking that rule is necessarily a serious offense. Harry's supposed breaches are seen as serious however because they also risk exposing the world of wizards to muggles, and that is treated seriously. Lily's breaches were presumably never that serious, possibly showing off in front of Petunia, but not much more.

Any sort of magic can be abused, such as say lifting something up above someone's head. The spell itself might be inocuous, but lets say she was keeping something out of Petunia's hands, or worse, lifted up Petunia's belt with her in it, it could indeed be a very serious offense, and the Ministry would not know the effects of what the spell she cast, only the spell itself. Its why the Ministry is so serious about any underage spell casting at all.

In "Philosopher's Stone" Aunt Petunia says that Lily came back from Hogwarts with frog spawn in her pockets and turned teacups into rats. If this is true, why wasn't Lily expelled?

Aunt Petunia is exaggerating a little; you have to allow for her state of mind when she started shrieking these things. However, just like her son, Lily was not averse to testing the limits of the Statute of Secrecy, so you can safely assume she will have had a few warning letters – nothing too serious, though.

Jo was actually asked this somewhere (sorry I looked and couldn't find it) but she said that Petunia was exaggerating. Though there probably is some truth there in my opinion. Would the ministry be able to detect the use of magical items? Like if Harry used the cloak at Privet Drive? Maybe Lily gave Petunia tea in one of those nose-biting teacups?

Yes, JK Rowling has confirmed this, that Petunia was just exaggerating about Lily. Petunia probably didn't know that underage wizards are not allowed to use macig outside of school, or she would've not been afraid of Harry in Chamber of Secrets.

How do you know she was underage?

Ah but there is a difference between underage magic in a magical household, and underage magic in a muggle household. In a magical household, the parents must notify the ministry of illegal activities, which the weasley parents may not have done

I am re-reading the series and I came across something that puzzled me. In PS/SS chapter 4 (?) "Keeper of the Keys" when Harry first meets Hagrid on the island and first learns he is a wizard we hear Petunia say about Harry's mother...

Explaining what a freak Lily was and that she would come home on vacation from "that school" and turn tea cups into rats and oh, how proud her parents were there was a witch in the family.

So Lily was performing under age magic. This means, most importantly, that whole permise that Uncle Vernon didn't know about Harry not being able to use magic @ Privet drive is false because Petunia would have known that Harry couldn't do magic away from school... unless Lily never got in trouble for doing underage magic @ her home away from school.