transient individual wrote:

I often go to the house of my friend where there are a lot of stray
cats. The super, or handyman of the building often sets up cages to
trap these stray cats and I think there is poison inside. He leaves
the cats locked inside the cages for 2 to 3 days after they ingested
the food, and then he lets them out. The cats are all wobbly when
released and look like they're about to die. is this against the law,
or are cats considered to be pests like rats?

As others have said it is animal cruelty I would contact the SPCA,
humane society or relevant authorities. You seem to be in Korea so I am
not sure who you have to contact.