Suppose an employee of a firm leaves it and joins another competing firm. The employee contacts his previous clients by calling them. He had the contact details of these clients in his brain (memory). These details are neither public information nor available with the new firm that he joins. He also did not copy the contact details of the clients from the database of his previous employer. He just uses his memory to contact this client.
Is he violating the Code and Standards of CFA Institute?
It’s been a while since I studied the ethics curriculum (5 years now).
I recall that your memory is your own. You are clearly not allowed to copy their information when leaving the company. So contacting them from your memory is not - in itself - a violation, if I remember correctly (though former employers of course won’t like it).
If they contact you, it is most definitely not a violation to talk to them, since the interests of the client precede the interests of your employer which precedes your interests.
Most employment contracts have statements about non-competes and not stealing contacts for a certain length of time. If your contract stipulates this, then the contract supercedes the standards of practice as long as it is not illegal or invovles misleading clients.