has_and_belongs_to_many - ensure only rows with there user_id are returned

[jmazzi]

Right now, im doing this in my controller:

@message = Message.find(params[:id],:conditions => ["user_id = ?", @session['user'].id])

Is there a way to do with in models them self so i dont have to pass in a user_id condition for all finds, deletes, etc?