I think you mean decentralised multi-stakeholders regulation rather than self-regulation. In that case, I agree, regulation should take place at the relevant level, which varies with the kind of market. However global markets have to be regulated at a global level.

And to insure fairness and transparency, the rules and methods for decentralised multi-stakeholders regulation must be defined and agreed at a global level.

"Dieu se rit des hommes qui se plaignent des conséquences alors qu'ils en chérissent les causes" Jacques-Bénigne Bossuet