Question: If a student always sits in [one] place from the seats in the class and he is known for this place and another student comes to sit in his place. Is it allowed for him to make the other stand and he sits in his place?
Answer: “Yes, if everyone has a specific place and someone comes to another place and sits in it. So the companion of that place can request him to stand. This is because everyone has a specific place. So him leaving off his place to sit in another place is not allowed for him unless he has the permission of the one who owns it. As for if he too does not have permission because those in charge want everyone in their place and they are known by a number which is written on the seat or a board in front of him and everyone is known by his name and number, then it is also not allowed to change the seat for his. Rather everyone sits in their place.
Likewise, if there are no numbers; however, everyone knows his place or the sitting is arranged and everyone knows his place and they are remembered in accordance to this arrangement, then they sit according to this arrangement. As for if the affair is not enforced and everyone can sit in any place he wants, then everyone sits wherever he wants”.
[Sharh Sunan Abi Dawood no. 548]
Faisal Ibn Abdul Qaadir Ibn Hassan