Rule 502: Students are not to give Peeves tools that assist him in being a poltergeist.
"Miss. Magdelin, I do not know how you were able to bring a muggle toy-"
"There is literally no security on the train. None. At all. Not 'gainst toys and none 'gainst muggle weapons now tha' I think 'bout it. I could bring a bomb and it wouldn' set off any alarms and that is rather alarming..."
*Sigh* "We will look into that. Now, about your actions? Giving that... thing to Peeves was incredibly irresponsible of you."
"Why? I was just bribin' him with it so as ta' not prank me this year. In fact, this was incredibly responsible o' me 'cause it was a way ta help me be less distracted an' allow me ta perform betta in school!"
AN: I picture the 'muggle toy' to be a water gun. Peeves would probably like that.