"BY ORDER OF THE HIGH INQUISITOR OF HOGWARTS
Teachers are hereby banned from giving students any information that is not strictly related to the subjects they are paid to teach.
The above is in accordance with Educational Decree Number Twenty-six."
-- Dolores Umbridge (OP25)
"Exploding Snap's got nothing to do with Defence Against the Dark Arts, Professor! That's not information relating to your subject!"
-- Lee Jordan (OP25)
By order of the Ministry of Magic, teachers were not allowed to give students any information except in subjects they taught.
- Lee Jordan joked in DADA class that Umbridge was not allowed by Decree 26 to "tell off" the Weasley Twins for playing Exploding Snap in class anymore because that was out of her area of expertise. Later, Harry saw Lee with his hand bleeding from a detention including Umbridge's black punishment quill, for which Harry suggested essence of murtlap (OP25).