Answer:
He uses a previous status of African Americans as evidence.
Step-by-step explanation:
The reason Judge Taney's arguments are ineffective is because he uses a previous status of African Americans as evidence which is not admissible because it is a previous status and not a current one.
Judge Taney wants to derive the and make certain the status of African Americans and how it is translated according to the Constitution to ascertain the rights and privileges they should enjoy which rendered his arguments ineffective.