Using Local Sourcing Rule For The Assignment Level Customer
The business requirement is to have B2B fulfilment flow for all its sales order (Internal or External B2B), hence all sourcing rules are defined as Local Sourcing rule, and at order entry the Ship from Warehouse is selected and apply the corresponding local sourcing rules.
However, there is a requirement of specific sourcing method (Buy from specific Supplier Site) for selected Customer or customer site. When we use assignment level as 'Customer' or anything that is combination of customer will not allow associating it to the local sourcing rule. Hence, the fulfilment method on this requirement is always treated as a Drop shipment.