legal membership bodies in most countries seems to have the potential to "get in behind" and support their members better than any trade union.
-IainB
I find this really insidious - I used to be a teacher in the UK and UK law now required teachers to be members of the state sponsored professional body - even to the point that the state pay the fees for teachers in full-time permanent contracts (it always annoyed me that I worked mostly on temporary contracts so I had to pay the bill personally).
Most professional bodies are little more than trade unions by another name - except that conservative politicians perceive them differently and encourage them (mainly because they become rich and power conservative bodies).
The main difference is that a trade union should (and I emphasise should because it rarely happens) represent their members' interests - in fact they usually represent some sort of political agenda more than their members, and are often part of the gravy-train syndrome.
Professional bodies are supposed to represent their profession - but what that boils down to is protecting the reputation of all lawyers/doctors etc (delete as appropriate) so that they end up defending almost any behaviour to avoid a scandal. It takes some extreme behaviour to get professional bodies to admit that a member has done something wrong and sanction them.
Ultimate both started from good and similar places but both have become corrupt because they are dominated by people who want power.