In the U.S., compliance with the ICH E6 guideline is regarded as:

In the context of clinical research in the U.S., compliance with the ICH E6 guideline is seen as voluntary for FDA-regulated drug studies. The ICH E6 guidelines, which focus on Good Clinical Practice (GCP), are designed to ensure that clinical trials are conducted ethically and that the data generated is credible and accurately reported.

While the FDA recognizes the ICH guidelines as a standard and recommends their use to promote the quality and safety of clinical trials, adherence to these guidelines is not legally mandated. Researchers and sponsors are encouraged to follow them, but ultimately, it is up to them to decide to comply. Therefore, compliance is a best practice that supports the integrity of clinical research and the protection of study participants rather than a compulsory requirement under U.S. law.