system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can illegal websites (i.e. piracy and illegal streaming) have advertisements on their sites of well-known companies and brands?

How can companies be allowed legally to do this and why doesn't this immediately expose these websites to the federal government?
gpt
If a site isn't based in the US they have no obligation to comply with US law. 

Most sites just sign up to an advertising service and then that service places ads on the site. Well-known companies & brands often have no ability to choose where there ads appear.