CIA forbidden by law to use sex/blackmail?

I was watching a show on Discovery channel about how various intelligence agencies used sex/seduction to gather intelligence. Seems a fairly viable tactic in the spook business, maybe overly romantisized/fictionalized by James Bond films and their ilk.

However, one thing that puzzled me was a guy saying up and down that the CIA does NOT do this because they are forbidden by law to do so. However, he didn’t explain WHY, and frankly it doesn’t make much sense, particularly for a country like the United States, which likely has many enemies (especially now).

They are forbidden by law from doing this because back in the 1950s-early 1970s, the CIA was accused of (and frequently guilty of) a number of frankly bonehead plots not simply aimed at gathering intelligence, but to actively overthrow foreign governments. You may have heard the joke about slipping exploding cigars into Fidel Castro’s humidor. It was at least seriously discussed, although IIRC the plan wasn’t attempted.

Every cite I’ve Googled for background on this is seriously biased either toward or against the CIA. This one http://www.spartacus.schoolnet.co.uk/USAchurchF.htm at least seems to give a relatively straightforward account of what investigations uncovered.