As a hotbed of illegal activity, how are flea markets allowed to exist?

I was just at my friendly neighborhood flea market for the first time in years and I was shocked at how much illegal activity there is going on there. There are people selling tobacco products when I highly doubt they have a tobacco license. Dvds and cds that when you open the box its just a copy burned onto a cd/dvd-r. Vendors selling k2 and salvia which are both illegal here. Extremely cheap name brand electronics and clothing that are either high quality imitation or (more than likely) stolen off the back of a walmart truck. Found a bin of make shift crack pipes and there was even a couple walking around the market carrying puppies and I saw them sell one for $300. I have a strong suspicion that if you knew who to ask you could quite easily procure child porn or heroin or any other illegal item there. Flea markets (in my experience) are quite blatantly black markets, the majority of all activity taking place is quite illegal. How do these not get shut down? This flea market has been around for as long as I can remember.