Carney quoted a March 2011 investigative report as saying that "the attorneys did not commit professional misconduct or exercise poor judgment, but rather acted appropriately in the exercise of their supervisory duties" in the New Black Panther case.
"After a number of past incidents of harassment of voting-section career staff based on perceived political affiliation, mostly occurring between 2004 and 2007, the inspector general reported that Mr. Perez has taken a number of steps to foster a more collegial and professional workplace," Carney told reporters on Monday.
The report said that Perez "restored nonpartisan, merit-based hiring to the Civil Rights Division" following the improper hiring practices of the Bush administration, Carney said.
Vitter pointed out that news outlets had reported that there were undercover investigations in Louisiana that led to a lawsuit saying that the state had violated voter rights by not ensuring that welfare recipients were given the opportunity to register to vote.
The law requires certain government offices, such as those that provide welfare assistance, to provide voter registration forms.
In that 2011 letter to Attorney General Eric Holder, he said the Obama administration hadn't shown any interest in enforcing the other side of the law that ensures that those who have died or are ineligible to vote are removed from the rolls.
The Justice Department must fully enforce this law, "rather than refusing to enforce the voter list integrity provisions while making the welfare agency registration law its top priority," Vitter wrote.
"The Civil Rights Division does not have the right to pick and choose which laws are worthy of enforcement and which ones are not."