Federal agents previously investigated the Southern Poverty Law Center's paid informant program for possible tax crimes, but the probe failed to yield any charges after Internal Revenue Service lawyers determined it was legally structured, sources familiar with the matter told CBS News.Agents from IRS Criminal Investigation in 2019 and 2020 homed in on shell bank accounts that a former chief financial officer at the civil rights nonprofit opened to pay informants in exchange for intelligence about hate groups. The agents sought to determine whether the SPLC unlawfully failed to file tax returns for those payments, sources said.But a Treasury Department...