After Harry's first minor violation—a Hover charm that was actually performed by Dobby the House-elf—he is merely warned. His second violation, blowing up Aunt Marge, is forgiven by Fudge because the Minister fears that Sirius Black is after Harry and feels that his safety after running away from the Dursleys takes precedence. After his third offence (creating a Patronus to protect himself and Dudley from two Dementors), the letter sent to him states that he is expelled from school, that representatives will arrive at his home to destroy his wand, and that he is required to appear at a disciplinary hearing, given that the offence occurred after he had already received one warning. Dumbledore reminds Fudge that the Ministry doesn't have the power to expel students from Hogwarts or confiscate wands without benefit of a hearing.