> The Federal government MANDATES fluoride.
Could you provide a source for that?
I did a Google-UncleSam search and read 40 CFR 141 and 142 on water quality regulations. The Feds do recommend Fluoride (as they do several other additives to water), but I did not find anything about them requiring it. They do require that if there is more than 4.0mg/l naturally occuring in the water, that the consumer be warned about the adverse affects to their teeth.
Interestingly, the DoD does require Fluoride in all water systems that they operate (mainly on isolated military bases), but this is not required when they buy from other water suppliers.
If they don't require it, how is this different from the other chemicals that local water supplies add in response to consumer pressure?
The same way the Fed mandate a 55 mph speed limit. The states had the freedom to set their own speed limits but would lose federal money.