system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How Do American ISPs Not Violate Antitrust Law?

I've heard countless stories about ISPs campaigning withing cities to not allow x competitor to offer their service. They're going directly to another source and directly requesting that xyz company be unallowed to compete, allowing them to maintain their monopoly. 

How is this not legally considered anti-competitive behavior? I'm not trying to circlejerk or anything, I just genuinely wonder what legal loophole allows them to do this.
gpt
Antitrust law is using your dominant position in one industry to suppress competition in another. It doesn't make it illegal to be ruthless.

In the U.S., most high speed Internet is provided by the same company that ran the physical wire to the building. If you live in a town with (for example) Cabletown as the major high speed ISP, it will be very hard for another company to offer a competitive product because they will have to run a cable. There is currently no requirement that Cabletown lease their physical line to another company. And Cabletown is well within its rights to argue against a city allowing another company to lay cable in their back yard. It's slimy, but not illegal.