In the common course of business, an advisor expects clients to come to them. It can be tempting to go down another advisor's client list and explain to each one how you can better serve them. Poaching clients like this isn't going to win you any friends among fellow advisors, though, and could get you into some legal trouble.
It's common to see lawsuits around accusations of poaching, most typically because an advisor left one firm and went to another, taking the client list with them. Such cases are successful when the original employment contract specifically states that an advisor cannot take information like a client list when leaving. Even if there isn't any such clause, though, some companies may still pursue a lawsuit. Your past employer may not expect to be able to get clients back, but it may hope to get some recompense for the loss of those clients.
Depending on the jurisdictions in which you work, the law can split hairs very finely. While an advisor who has signed a contract with a non-solicitation clause before moving on to another company may not suggest to clients that they follow, it is often fine to announce the move and allow clients to make their own decisions. If a client chooses to follow you, rather than is asked to follow you, it is ethical and legal to continue working with that client at your new employer.
It's crucial to check the local law and make sure that you have the most up-to-date information about what actions you can take. You also need to read through any contracts you sign, possibly with the assistance of a lawyer. Laws can change almost overnight, as it did in Texas in 2011, when the Texas Supreme Court overturned a previous decision of its own, effectively making non-solicit clauses easier to enforce. Furthermore, some employers will terminate new employees who have been found to behave inappropriately, in terms of attempting to poach their former employers' clients.
Is It Worth It?
Even if you worked hard in the first place to land the clients you want to take with you, they're unlikely to be worth the cost of a lawsuit. You're certain to burn bridges with your former employer and, depending on what you have to do to get a copy of your client list to take with you, you could do serious damage to your reputation.
However, non-solicitation clauses usually have a time limit attached, after which, the decision to try to win over clients of a past employer becomes one of ethics, rather than legality. As long as you don't need to do anything underhanded to get information about the client, it comes down to a question of who the client prefers to work with – something that may create some sore feelings but certainly isn't a matter for an ethicist.
The Bottom Line
Poaching clients from an advisor you haven't worked with in the past is a much more difficult proposition: Unless you have access to the client list, there's no way to directly target the clients. Getting access to the client list usually requires unethical or illegal behavior. Such actions would certainly open you up to a lawsuit. You may be able to compile a partial list from the company's social media presence or website, but you may not get much more than you would through other marketing methods. It's acceptable to contact these prospects through normal channels and make your pitch for their business.