Opponents of Arizona’s hard-line immigration enforcement law are using emails sent by a former state senator who championed the law to support allegations it was racially motivated.

The American Civil Liberties Union obtained thousands of Russell Pearce’s emails through a public records request.

They’re part of a new legal effort by civil rights groups to block police from enforcing the Arizona law’s so-called “show me your papers” provision recently upheld by the U.S. Supreme Court.

The Arizona Republic reports that the emails — which include messages sent to and from Pearce — blur lines between undocumented immigrants and Hispanics in general. The ACLU says the emails show a striking hostility toward the Hispanic population. The ACLU is including the emails in a court request asking U.S. District Court Judge Susan Bolton to block parts of SB 1070 from taking effect.