Protected term

A protected term is a phrase, or more commonly a title, that has restrictions and requirements as to who may use it. Generally, such terms are protected in that an individual or organisation must have the express permission of a governing or controlling body in order to use the term, and is usually dependent on having obtained specific qualifications or completion of the required recognised training.

Because protected terms are regulated by law, they will vary from jurisdiction to jurisdiction.

Examples
Most people are familiar with the concept, even if they are not aware of the phrase itself. For instance, most people know that any old punter can't just start using the following:

Titles

 * Medical Doctor
 * Naturopathic Physician (in American states and Canadian provinces where Naturopathic Medicine is regulated)
 * Nurse
 * Dentist
 * Police Officer
 * Judge
 * Dietician
 * Professor
 * Member of Parliament
 * Senator
 * Congressman
 * Military ranks
 * Chiropodist and podiatrist, in the UK
 * Social worker, in England
 * Speech therapist/speech and language therapist, in the UK
 * Pharmacist, in UK
 * Physical therapist and physiotherapist, in the US
 * Professional engineer, in the US and Canada
 * Psychologist, in the US and Canada
 * Lawyer

There's also some more niche titles protected in the UK, like art therapist, dramatherapist, and various psychological specialisms.

Others

 * Organic
 * Fat free, sugar free
 * Champagne, Scotch, Bordeaux, and many, many other alcoholic beverages with a regional or national identity.

Non-protected terms
There are two tactics the woo industry and the anti-science religious community have discovered to get around this problem. First, by being less specific, you can imply a whole lot and not legally cross the line. Any ol' "doctor" (of literature, or underwater basket weaving) can use the term "doctor". If you are talking nutrition, theology, or how evolution clearly violates the Second Law of Thermodynamics, and sign your posts "Dr. Soandso", most readers will assume your doctorate is actually in the field you are pontificating in. Ah, the joys of ambiguity!

The second trick is to simply invent a variety of official-sounding terms, which have no officially recognised meaning. This is rather fortunate, as anyone can use them. Even better? Provide schools that offer specialist degrees in your new field so they too have access to your new term.

Such non-protected terms are completely meaningless, just a ruse to convince gullible punters that the snake oil salesman in question is a trustworthy and knowledgeable chap. Bad Science author and blogger Ben Goldacre decided to figure out exactly what level of study was needed to get such a certification. By simply lightening his pocketbook, he managed to get his dead cat endowed with the title "nutritionist".

Titles

 * Nutritionist
 * Homeopath
 * Psychic
 * Minister
 * Shaman, Medicine Man, Pipe Carrier
 * Psychologist in the UK, although specialisms like clinical psychologist and educational psychologist are protected

Other terms

 * Natural
 * Healthy
 * Whole grain
 * Low fat
 * "Scientifically proven to..."
 * Light/"Lite."

But pay attention to the protector
Just because an organization owns a term and restricts its use, doesn't mean the people allowed to use the term are held to any kind of rigorous standard.

For example, the term "Dietitian" is protected by the Academy of Nutrition and Dietetics, and to earn that title a person needs to have completed an accredited bachelor's degree, a 6-12 month ACEND-accredited supervised practice program, a passing grade on a national exam, and recent continuing education. All in all, it's a pretty strict standard. The term "Certified Nutritional Consultant", on the other hand, is protected by the American Association of Nutritional Consultants, and has been awarded to deceased cats and sheepdogs.

Table of protected titles
The following table lists various titles and records who they are protected by. An X indicates where something is not a protected title. Because the table is not complete, some entries are left blank; this indicates information has not yet been added and no further implication should be drawn.

Protecting bodies:
 * AHPRA - Australian Health Practitioner Regulation Agency
 * GCC - General Chiropractic Council (UK)
 * GOsC - General Osteopathic Council (UK)
 * HCPC - Health and Care Professions Council (UK)