According to a 2014 paper by US law professor:

many WTO violations take place in the interstices of law, areas where government officials exercise discretion: whether or not to register a foreign company, to issue it a business license, or to prosecute someone for IP theft. Likewise, China distributes trade regulations to governmental agencies as “internal guidance” (neibu cankao) that should be published under China’s WTO transparency obligations, but in fact never are. The [WTO] dispute settlement system provides a very rough tool by which to reshape a member’s domestic legal system and to monitor its implementation of WTO commitments. A range of violations takes place, either below the radar or without meaningful recourse for investors or manufacturers outside of China.

What's the evidence that China did or does pass such publicly undisclosed trade regulations?