49 CFR §375.515

1. (a)If an individual shipper elects not to observe a weighing, the shipper is presumed to have waived that right.
2. (b)If an individual shipper elects not to observe a reweighing, the shipper must waive that right in writing. The individual shipper may send the waiver notification via fax transmission; e-mail; overnight courier; or certified mail, return receipt requested.
3. (c)Waiver of the right to observe a weighing or re-weighing does not affect any other rights of the individual shipper under this part or otherwise.