As already answered, yes, sometimes that's the kind of contract brokers have, where cliemts give them idscretion to manage their money as they see fit. You need to see a lawyer ASAP since your statute of limitations for breach of contract in TX is 4 years, and you may not have a claim anyway since your broker would not have had any way of knowing that the market would crash.
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Whether the broker can do this is dependent on the relationship you had with him/her. Was your account discretionary or non-discretionary? Was it a straight brokerage account or was it an account with a management fee? Market losses alone are not enough to claim damages. You need to show that the broker violated one of the duties owed to you. Have you complained to the firm or the broker? Why has it taken four years?
With respect to applicable law, TX law may apply but you likely signed an arbitration agreement with your broker's firm when you opened the account. This would mean that you agreed to arbitrate your claim before FINRA. Arbitration is not like court but don't be fooled - you'll need an attorney.
The foregoing is not legal advice nor is it in any manner whatsoever meant to create or impute an attorney/client relationship.
If your account agreement with the broker-dealer says that you gave the broker discretion, then he or she can make trades without your prior consent. However, discretion doesn't mean that the broker can do whatver he or she wants. All brokers are bound by the suitability rules, which require them to inquire into your investment objectives, risk tolerance levels, experience and financial ability to sustain loss. All recommendations and trades must be appropriate for you, given those factors. If the funds sold were less risky than the stocks that were purchased, and the new risk levels in your portfolio exceeded what was suitable for you, then you may have reason to gripe. Griping means filing an arbitration claim with FINRA. And yes, you should talk to an experienced FINRA arbitration lawyer before deciding whether to do that.