Federal authorities said they arrested 18 people Wednesday on charges related to selling illicit drugs including fentanyl and methamphetamine around a Los Angeles park. The area, called MacArthur Park, is a densely populated immigrant neighborhood west of downtown LA where federal immigration authorities and the National Guard made a brief but mighty show of force last summer. In this week's raids, authorities seized 40 pounds (18 kilograms) of fentanyl from a single home, the U.S. Attorney’s Office said. Two of the people arrested, a couple from South Los Angeles, are believed to be the main sources of those drugs sold in the park, which were stashed in storefronts and distributed to street-level dealers, authorities said. “We're here today because California policy has failed,” First Assistant U.S. Attorney Bill Essayli said during a news conference announcing the arrests.…