President Obama on Monday nominated civil rights attorney Thomas Perez to be his next labor secretary, a move already drawing complaints from Republicans.

Perez most recently served as the assistant U.S. attorney general for civil rights, a division that came under fire in recent days when conflicts between liberal and conservative factions there were highlighted by an auditor. The investigator also questioned Perez’s truthfulness in describing the department’s decision to drop a voter intimidation case involving the New Black Panther Party.

And some Republicans are calling for a congressional investigation into whether the Justice Department made a deal with the city of St. Paul, Minn. to withdraw from a Supreme Court housing discrimination case.

If confirmed, Perez would become the lone Hispanic in Obama’s cabinet, replacing Hilda Solis. Perez is highly popular in the labor community and has built a reputation for pursuing voting rights cases.

Perez formerly served as secretary of the Maryland Department of Labor, Licensing and Regulation but for Washington-area residents, he’s most known for his stint on the Montgomery County Council. Perez was on the body from 2002 to 2006 and represented the greater Silver Spring area.

But that local work hasn’t gone unnoticed by critics.

Sen. Jeff Sessions, R-Ala.,  hammered Perez on Monday for his time at Casa de Maryland, a Hispanic-rights advocacy group that Sessions said “instructed illegal immigrants on how to escape detection, and also promoted illegal labor sites and driver’s licenses for illegal immigrants.”

“This is an unfortunate and needlessly divisive nomination,” Sessions added, calling Perez’s views on immigration “far outside the mainstream.”

And Sen. David Vitter, R-La., vowed to block the nomination.

For his part, the president called Perez an advocate who “fought to open pathways into the workforce for everyone willing to contribute, including people with disabilities, LGBT Americans, and immigrants.”