I live in the Great State of California... so yeah- if it can be regulated, it is. Our state is working on making Soda illegal, so soon this C02 gas is going to explode in prices.And I also use metric like there's no tomorrow, so take that you 'merican...
Regs can of course change from country to country (in your case even from State to State) and be more or less stringent accordingly. Residual valves might or might not be mandatory, traceability might or might not be mandatory, filling stations might or might not have to be designed and operated so that no contamination can be dragged into the bottle during filling (which might or might not require evacuating all lines with a vacuum pump prior to commencing filling) and so on and so forth.
One principle is more or less universal though. If somebody dies (or at least gets seriously ill), somebody else might have a problem...