This reconstruction era policy gave voting rights only to people whose grandfathers had been legally allowed to vote, thus excluded freedman from voting

The given statement explains Grandfather Clause  

Explanation:

The Grandfather Clause was a legal or protected instrument passed by seven Southern states during a recreation to deny suffrage to dark Americans. It implied that the individuals, who had delighted in the privilege to cast a ballot preceding 1867, or their lineal relatives, would be absolved from instructive, property, or duty necessities for casting a vote. Thus, regardless of whether they met every one of the prerequisites, they were not permitted to cast a vote.