After the obligor receives the notification of transfer ofthe obligee's right, the obligor may claim its demur against the assignor to the assignee.
第八十二条债务人接到债权转让的通知后,债务人对让与人的抗辩,可以向受让人主张。
2
When the assignment is invalid, obligor has the right to restitute from assignee those obligor gives to theassignee and in theory the right is the claimof property right or unjust enrichment.