Bitcoin regulations are possible and even realistic for centralized exchange platforms, such as for example bitstamp, virtex, or kraken, that send and receive fiat money through the banking system.
Regulation do not necessarily reach peer to peer exchange platforms (p2p). Since such p2p platform relegates the actual exchange to the two individuals selling and buying, it does not perform regulated acts itself. Concerning the two individuals trading, there are no regulations that apply across the globe to individuals trading from their own country.
But then again, the fiat to bitcoin exchange is not the essential bitcoin act.
The essential bitcoin act takes place when the bitcoin miners decide to add a signed bitcoin transaction to a block and decide to store this block in the blockchain.
The bitcoin miners apply pre-established rules when performing their core job and do not listen to anybody at all while doing so.
No regulator on the globe, in any of its 200+ jurisdictions, should ever hope that the cryptocurrency miners would listen to him. If a majority of any cryptocurrency mining community ever did so, its users would immediately repudiate their miners and join an alternative cryptocurrency. It would definitively crash the value of the cryptocurrency and effectively destroy it.
Regulators should understand that something like bitcoin only has value, exactly because its miners do not listen to them. In other words, the true, unique selling proposition of bitcoin lies exactly in the fact that regulators are being neutralized. Without regulators, there would be no need for bitcoin, and therefore bitcoin would not even exist.