Let's be clear:
1. The common rulebook for goods would touch only a small part of policy. The UK government, as it did in the EU, will determine the vast majority of issues that citizens care most about. Talk about dictatorship is sloppy hyperbole.
2. Under the Chequers compromise, the government reserves the sovereign right to veto or depart from any regulation it deems unacceptable. Whether the EU accepts this is another matter.
3. Even if there is no formal agreement, governments will always be under strong economic pressure to follow the preferences and regulations of more powerful players - whether it is big business or other governments. Is that any less of a dictatorship to use your words?