I think we are in danger of over thinking this.
Let me put to you what companies do and you decide who ethical companies are.
Manufacturer A is a niche market single product manufacturer who depends on agents and distributors round the world to include his product in their portfolio.
As the years go by the various agents and distributors built the market for the manufacturer until they have very significant sales globally.
Then they are bought by a major global single source company.
The new owners do nothing immediately because, despite having their own sales offices in most of the affected countries, there will be an "acclimatisation period".
But, because of the Arab Embargo or company policy or some such nonsense, they require that in future instead of the distributors simply ordering product they must now declare the application and the end user.
At the end of the year, or maybe 18 months, they pull the plug on all the distributors. In that one year they have obtained a very clear picture of who the major clients are and the key applications.
The distributors are left with enquiries but no product and no alternative product to offer.
Now though the agents and distributors may all cry "Foul!" no one takes any notice.
Most companies are realistic.
As I said above, most salesman are more highly valued for their contact lists than anything else.
The only two times I have ever know action to be taken was when, believe it or not, an employee at one company was also in the pay of a competitor and passing information directly to them.
What happened I don't know. Anyone stupid enough to do this obviously leads a Walter Mitty life style and needs treatment.
The second instance was when the local chamber of commerce wrote a snotty letter to a company about their marketing manager posing as a client and trying to obtain their competitor's prices.
Not sure what they were complaining about unless it was the subterfuge he resorted to. Most companies have and need to have a pretty good idea of competitor pricing and how they get it is to ring up and ask or get other people to ring up and ask.
Ethical?
Who knows. In the purist sense none of it is.
What is more to the point is that this is how all companies behave in order to survive. They all know this is what they are doing and what the others are doing to them.
That you may have a contact list is one thing. How you use it is another.
To use it to seek business in a fair and competitive way is one thing.
To use it to blacken or malign the former employers name or anything else is something else again.
To expect some one to throw away their contact list and go through a charade of looking surprised to find the company they visited twenty times a year for their original employer is unreasonable.
In this area I suggest that it is reasonableness that should rule, not some abstract EU court of Human rights approach to impose something idealistic and unworkable on the real world.
JMW