Follow up to the Wikipedia definition of professional.... In the second paragraph, they reference "guilds".....
 
Here is a portion of the Wikipedia definition of "guild"..... More interesting stuff..... Notice they refer to the AMA, ABA, Realtors and Screen Actors Guild.... Don't see ALPA there.... In fact only 3 of the aforementioned are unions......
 
 
 
Influence of guilds
Guilds are sometimes said to be the precursors of modern 
trade unions, and also, paradoxically, of some aspects of the modern 
corporation. Guilds, however, were groups of self-employed skilled craftsmen with ownership and control over the materials and tools they needed to produce their goods. Guilds were, in other words, small business associations and thus had very little in common with trade unions. If anything, guilds were more like 
cartels than they were like trade unions (Olson 1982). However, the journeymen organizations, which were at the time illegal, may have been influential.
The exclusive privilege of a guild to produce certain goods or provide certain services was similar in spirit and character with the original 
patent systems that surfaced in England in 
1624. These systems played a role in ending the guilds' dominance, as 
trade secret methods were superseded by modern firms directly revealing their techniques, and counting on the state to enforce their legal 
monopoly.
Some guild traditions still remain in a few handicrafts, in Europe especially among 
shoemakers and 
barbers. Some of the 
ritual traditions of the guilds were conserved in 
order organizations such as the 
Freemasons. These are, however, not very important economically except as reminders of the responsibilities of some trades toward the public.
Modern 
antitrust law could be said to be derived in some ways from the original statutes by which the guilds were abolished in Europe.
[edit] Modern guilds
Modern guilds exist in different forms around the world. In many European countries guilds have had a revival as local organisations for craftsmen, primarily in traditional skills. They may function as fora for developing competence and are often the local units of a national employers organization.
 
In the 
United States guilds exist in several fields. The 
Screen Actors Guild and 
Writers Guild of America are capable of exercising very strong control in 
Hollywood because a very strong and rigid system of intellectual property respect exists (as with some medieval trades). These guilds exclude other actors and writers who do not abide by the strict rules for competing within the film and television industry in America.
 
Quilting guilds are also very common and are found in almost all areas of the United States.
Real estate brokerage is an excellent example of a modern American guild. Telltale signs of guild behavior are on display in real estate brokerage: standard pricing (6% of the home price), strong affiliation among all practitioners, self-regulation (see 
National Association of Realtors), strong cultural identity (see 
Realtor), little price variation with quality differences, and traditional methods in use by all practitioners. In September 2005, the U.S. Department of Justice filed an antitrust lawsuit against the National Association of Realtors challenging NAR practices that, DOJ asserts, prevent competition from practitioners who use different methods. The DOJ and the Federal Trade Commission in 2005 advocated against state laws, supported by NAR, that disadvantage new kinds of brokers. For a description of the DOJ action, see 
[1]. U.S. v. National Assoc. of Realtors, U.S. District Court Norther District Illinois, Eastern Division, September 7, 2005, Civil Action No. 05C-5140.
The practice of law in the United States is also an example of modern guilds at work. Every state maintains its own 
Bar Association, supervised by that state's highest court. The court decides the criteria for being admitted to, and remaining a member of, the legal profession. In most states, every attorney must be a member of that state's Bar in order to practice law. State laws forbid any person from engaging in the unauthorized practice of law and practicing attorneys are subject to rules of professional conduct that are enforced by the state's high court.
 
Other associations which can be classified as guilds, though it isn't evident in their names, include the 
American Medical Association and the 
American Bar Association.
 
Scholars from the 
history of ideas have noticed that 
consultants play a part similar to that of the journeymen of the guild systems: they often travel a lot, work at many different companies and spread new practices and knowledge between companies and corporations.
 
Many professional organizations similarly resemble the guild structure. Professions such as architecture, engineering, and land surveying require varying lengths of apprenticeships before one can be granted a 'professional' certification. These certifications hold great legal weight and are required in most states as a prerequisite to doing business there.