Beginning 1 September, we will need to geoblock Mississippi IPs

Clueless human, but what stops a company from ignoring these laws from certain states? How is this enforceable if a company doesn't have any infrastructure within that state?

Apparently, U.S. statutory and case law establish that a business has an "economic nexus" in a state can be made subject to that state's laws. An economic nexus doesn't require a physical presence, just sufficient economic activity. Sufficient economic activity is usually defined, by each state, according to revenue or volume of transactions. Another test for an economic nexus is something called purposeful availment, which is whether a business is targeting the residents of a jurisdiction. So it seems like, "Are you intentionally selling to Missouri residents?"

To enforce all this, states can sue companies and they can take steps to ensure companies can't do business in their state (so like maybe force ISPs to block Dreamwidth?).

Iirc, there was case law where a site was successfully found guilty because the site allowed ads, and the advertisers were targeting based on ip location. Not the site! The site didn't even log that data. But the ads were used as the vector of purposful availment.

When I get the time, I'll be hosting a site from my closet that allows anything short of csam and I will reject states like MS and TX. My final act will be to die. But I don't much want to live.