Acupuncture relieves pain. Exactly how acupuncture needles in the skin achieve pain relief is not known and is not easily testable. If acupuncture cannot be tested by standard clinical experiments then Western medical regulators will remain loath to certify it as a legitimate medical treatment.
Clinical tests may require one group of patients to receive a treatment, one group to receive no treatment, and one group to receive a harmless placebo treatment. There is no placebo treatment for acupuncture, as puncturing the skin with needles always has an effect. It is also hard to define the correct acupuncture test treatment to give to a test group, as acupuncture treatments are designed for individuals in the context of a holistic therapy program; it is not like prescribing a specific dosage of a drug to counteract an illness, regardless of the patient's personality.