Educational Decree Number Twenty-eight

This decree allowed Dolores Umbridge to replace Albus Dumbledore as Headmaster of Hogwarts (OP28).

• Dolores Umbridge, along with Minister for Magic Cornelius Fudge, his assistant Percy Weasley, and two Aurors, Dawlish and Kingsley Shacklebolt, confronted Dumbledore in the Headmaster's Office with the member list of Dumbledore's Army, an illegal group. Harry and Minerva McGonagall were also present.
• A wizard named Willy Widdershins had been given a plea deal with the Ministry after getting arrested for making exploding toilets, and testified to being present at the Hog's Head tavern during the first meeting of Dumbledore's Army  (OP22, OP27).
• Ravenclaw Marietta Edgecombe had also confessed to Umbridge that the group secretly met in the Room of Requirement, and Inquisitorial Squad member Pansy Parkinson was the one who found the enchanted parchment signed by all the members.
• Hermione had enchanted the parchment to give any traitors a Snitch Jinx, and Marietta broke out in pimples that spelled "Sneak" across her nose for betraying the group to Umbridge.
• With Shacklebolt's help in silently Obliviating Marietta's memory, and taking all the blame for himself so the members wouldn't be punished, Dumbledore grabbed Fawkes and disappeared from the room "in a flash," causing the portrait of Phineas Nigellus to say "'You know, Minister, I disagree with Dumbledore on many counts… but you cannot deny he's got style…" (OP27).
• Umbridge was then made Headmistress of Hogwarts, and the Weasley Twins escalated her problems with their Portable Swamp and their special Weasley's Wildfire Whizbang fireworks. The Hogwarts teachers who despised Umbridge refused to help her make any of it go away (OP29,OP30).
• Decree Twenty-eight was abolished when Dumbledore returned to the school after the Battle for the Department of Mysteries, and he was reinstated as Headmaster (OP36).

The Hufflepuff ghost called the Fat Friar told Ernie Macmillan that the gargoyle's outside Dumbledore's office wouldn't allow Umbridge back inside, and she "had a right little tantrum"about it (OP28)

Draco Malfoy overheard Ernie and the Gryffindors talking about Umbridge and decided to dock points from them in his role as member of the Inquisitorial Squad:

" ... so, Granger, I'll have five from you for being rude about our new Headmistress. Macmillan, five for contradicting me. Five because I don't like you, Potter. Weasley, your shirts untucked, so I'll have another five for that. Oh yeah, I forgot, you're a Mudblood, Granger, so ten off for that."