wont find legal representation? a lawyer cleans your shoes if the money is right. i never heard a lawyer saying "save the money we cant sue on this case".
trust me, you will always find a lawyer. and a lawyer always finds a reason to sue someone.
anyways. brokers (depending on the country you come from) are liable to stick to the laws and regulations of their country of business. in pretty much all countries i know the regulations are that the client must be informed about "xyz" (usually risks) but nowhere that a client must be refused by any other reason than that he is not 18 or (thats a big "or", since we are not debating this topic here) the client tries to engage a european brokerage while he is a USA tax liable person (then problems can occur, but those can be solved as well). or- (thats a big "or" as well) the client might be engaged in money laundring for specific entities/persons (government sanctioned people like moscow politians sanctioned from US/EU governments) or the client might be associated with money laundring/financing terrorist entities.
the only reason your broker can refuse to pay you out is if you falsified your documents (ID), opened a bank account on a invented person or entity, you evidentily frauded your broker (must be proven by broker). But even on falsified ID or issues regarding USA tax liability the broker can not (and will not have any interests) in banning you from withdrawing funds. he will have interests in getting rid of you as a client and forcefully close your account and pay you out the balance (including all gains/profits you made). if you falsified your ID, all you need to do is prove who you are and that you are not on the US/EU sanction list, not associated with terrorism or funding such style, that you are not associated on interpol with financing/money laundring of criminal organisations- and your broker will still oay you out with all your profits.
my comment about the big four is what hurts the brokers. nowadays you cant operate any public listed company without beeind audited by one of the big four. once one of them puts a broker on a "difficult list" banks will stop making business with that broker.
and now just to make sure i dont catch "smart" comments like "brokers refuse you if you dont have 50k or some regulatory necesarry documents"- we are exclusevely talking about retail client brokers here. not about the real brokers.