I was curious about the source of Facebook's liability. It turns out their liability stems from the Fair Housing Act (FHA), 42 U.S. Code § 3604(c) (https://www.

I was curious about the source of Facebook's liability. It turns out their liability stems from the Fair Housing Act (FHA), 42 U.S. Code § 3604(c) (https://www.law.cornell.edu/uscode/text/42/3604 https://www.law.cornell.edu/uscode/text/42/3604) which has been repeatedly interpreted over the years to apply to publishers directly. Facebook has a duty to screen housing advertisements for discriminatory indications or intent. The question of whether this sort of disparate impact discrimination meets the criteria for 3604(c) is a different matter. (My uninformed guess is that it does not, but Facebook is being attacked on all sides so will probably be judicious regarding when and how hard it pushes back.)