There's no readonly possibility on the calendar view so the only way to prevent updating a done or cancelled transfer is to raise on the write. We should to raise in the inverse function so that it is possible to bypass the constraint by writing directly on the move, as we want to change some date in the demo data. closes odoo/odoo#36550 Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>