Whilst way you say may technically be true, the government could just declare this:

Each person must publicly declare the bitcoin addresses that they hold. Any legitimate business accepting payment in bitcoins can only receive bitcoins from other registered addresses, else they are black flagged and no longer a registered address.

Now, your average business and the banks are not going to circumvent these rules. The Banks will probably give their business customers payment gateways that enforce these rules without the business having any choice. Black market bitcoins will still exist, they will just be useless as "normal" currency and will be completely separate, with no way to cross over. Since all transactions are public it is trivial for the government to enforce these rules.

You'll still be able to run your exchange in some other political jurisdiction, but unless the Government white lists your addresses, nobody will be able to spend those coins on legitimate businesses in your country.