The ADL maintained its close relationship with the FBI through the rest of the century, even during moments of tension—as in 1993, when the FBI's search for a stolen FBI file in the Jewish organization's possession eventually led to a San Francisco Police Department raid on ADL offices. Police wound up discovering an ADL surveillance operation targeting a host of leftist organizations—including Arab, Black, Jewish left, and anti-apartheid groups—and the FBI briefly investigated the matter before closing its inquiry in 1994.

TI-fucking-L. Funny detail from the second article:

The ADL operatives even spied on a handful of U.S. Congressmen, all Democrats, including Nancy Pelosi

Definitely recommend reading the second article which details the ADL's illegal surveillance operation and cooperation with apartheid South Africa (and how they got off with barely so much as a slap on the wrist).