Medical assistants collaborate with the doctor according to the needs and the law and often rely on a cooperation agreement with a doctor describing the specific activities of a person working in a given medical practice. Supervision requirements focus on the need for a written cooperation agreement with a physician that can describe the procedures that a medical assistant can perform. State policy determines whether the supervisory relationship between the medical assistant and the doctor is established at the level of practice (within the medical practice where the medical assistant will practise) or by the National Order of Physicians or in national law.