OpenAI is initially restricting access to the textGrain detector to approved researchers and expert organizations on a case-by-case basis under the European Union's Code of Practice

From the articleOpenAI will watermark ChatGPT text in the EU but makes it optional for API users worldwideAlso in OpenAI is adding text watermarking in ChatGPT and Codex, OpenAI will start watermarking ChatGPT’s text in the EU