UK legislation is generally 'permissive' and, as such, the title "engineer" is not protected by law therefore anyone can call themselves an "engineer" or "professional engineer" or "registered engineer" and many semi-skilled and unskilled trades adopt this title. However the 'professional' titles awarded by the Engineering Council are protected by law. Registration as a chartered and incorporated engineers or as engineering technicians is voluntary and candidates are required to demonstrate a high standard of professional competence acquired through education, training and responsible experience in order to register. There are four categories of registration: