Row level permissions in screens

[taiwanleaftea]

I have users and some items, stored in "items" table. Items table has column "user_id". The user can edit only those items that belong to him.
I can get user's items with Auth::user()->items()->get(), and I can check if the item belongs to user using $item->user_id === Auth::user()->id
Where in the edit screen is better to do this check?