The CBA defines being in the legal profession as basically having already joined a legal club (well, they wouldn't put it that way, but I'm simplifying things here because I assume your question is how this could relate to the SEO industry)
In this case, unless you can show your enrollment in a pre-approved organisation - ie a law school, the Alberta Bar, etc, then you can't get in. So it's easy for them because they put all the onus on the other groups to keep their membership in line.
The CBA has it's ownCode of Conduct
which basically boils down to the protection of the public interest. Most of the Local Bars have taken it's Code either in toto
or for the most part. Since it has it's own Code, you can be kicked out if you are bad, though usually by that time you've been kicked out of the local Bar and the point is moot
Remember that lawyers make rules for everything, but by the same token, if you think the ethics debates in this forum are interesting, you ought to hear the pros do it LOL The result is a set of rules that basically boil down to serve the public interest, protect your clients, and don't do things that would bring the profession into disrepute.
As for the fees - the members section of the website contains audited financial statements and if you check the website www.cba.org you will see that almost every single link relates to legal education and advocacy in some way. I imagine that the equivelent sites for England, the US and elsewhere are similar. Remember lawyers have had a lot of years to practice, and the profession tends to attract , errr, well, nitpickers
It may not be the best template, but there are worse ones.
At the moment, the standards of SEO Consultants seems quite good, if you couldn't join SEMPO unless you belonged to SEO Consultants or a similar organisation, then that may solve many of the worries I see showing up here. I'd advise against giving anyone a virtual monopoly on anything, but if SEO Consultants is watching SEMPO and vice versa, they are less likely to get into trouble - kind of like the senate vs the house of representatives in the government
I don't know if there should be a way to FORCE anyone to join anything like they do in the legal profession (after all, it's not like you might get the electric chair if your SEO screws up), but it would be nice to have the option if this appeals to you. I'd be pretty suspicious of any company who would pay to join SEMPO but was rejected as a spammer by SEO Consultants.
BTW, I'm NOT a member of either group, and will only join if I feel like it. But I wouldn't have a problem with it, either. I'm not on a membership drive, but at the same time it would be nice to be self regulated. Frankly, I'd like my clients to know I'm an upstanding guy, and who better to judge that than my peers? After all, I could fool a client, but you guys? Not for long...
One final point - although belonging to the CBA looks nice, it doesn't get you big points by itself - it just shows you are interested in the legal community. It's the combination of having met the professional standards of the (in my case) Alberta Bar PLUS the interest in the public welfare role the CBA offers. In short, you have to prove you are compliant and capable first, THEN demonstrate an interest in ethical behavior and community involvement to get the whole package. Many don't care to try.
Hope that helps,