"Not another one!"
-- Minerva McGonagall (OP19)
Educational Decree Number Twenty-five gave the Hogwarts High Inquisitor (Dolores Umbridge) “supreme authority” over all punishments at Hogwarts.
Decree Twenty-five gave Umbridge the ability to overrule other teachers on matters of discipline (OP19).
Reasoning and implications
Umbridge went to the Minister for Magic Cornelius Fudge to get more control after Dumbledore allowed the Gryffindor Quidditch team to reform after she disbanded it (OP19).
Once Umbridge had the power to overrule both Dumbledore and Professor McGonagall, she banned Harry and the Weasley twins from playing Quidditch “ever again” after they fought with Draco Malfoy after a match (OP19).
From the Web
Writing by J K Rowling on Pottermore: Dolores Umbridge
Pottermore feature: Dolores Umbridge
Harry Potter Wiki: Educational Decree Number Twenty-five
Tags: authority banned control cruel detentions discipline fight laws punishment rivalry rules