How can a person coming from a sanctioned country invest for their retirement abroad?

I realize this may be a difficult question without further details, but I'm hoping someone with experience in cross-border investing or changing residency status might be able to share some insights. How are long-term investment accounts typically affected when an investor's legal residence status changes? For example, if someone is investing through a brokerage in their country of residence and later loses the right to reside there (due to a job change, visa expiration, relocation, etc.), what