The Chinese central bank required bitcoin exchanges to suspend withdrawals until compliance systems were updated. Trading on the exchanges fell off a cliff, but resurfaced on less formal over-the-counter venues like LocalBitcoins, a site where users post “advertisements” -- like on Craigslist -- to buy or sell bitcoin for local currency.
Blocking LocalBitcoins would be no solution, in part because people can use virtual private networks to access it anyway. Also, plenty of trading happens on lesser-known sites and on micro-messaging services such as WeChat and QQ. The latter already have their own payment systems, allowing users to build chatbots to automate trading activity. For those who prefer a more familiar trading interface, decentralized exchange software such as Bitsquare can construct an order book based on outstanding offers accumulated from other participants.