For legal help, seek the regulatory bodies in each country you're interested in

For example, if you buy US stocks via IB, and you want to know your legal rights
- they are a member of FINRA https://brokercheck.finra.org/firm/summary/36418
- FINRA has safety nets when brokers that are part of FINRA disappears http://www.finra.org/investors/alerts/if-b...loses-its-doors
- you can transfer stocks from one broker to another with ACATS https://www.interactivebrokers.com/en/softw...tstransfers.htm