ISPs blocking would be a severe action, probably violating “common carrier” laws. They’d be sued, customers would switch providers, and (acting as originally designed) internet would largely route around blockage. Worst case, there’d be a market for new non-censoring ISPs & backbones; some viable & interesting tech is waiting for the opportunity.
Worst case, there’d be a market for new non-censoring ISPs & backbones;
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Most ISPs are just bandwidth resellers. Telecom backbones on the other hand are not very dynamic. Like changes in the energy sector, new communication paths require planning and capital