The question was answered as shorting not NSS. To suggest the question included NSS is not realistic.
A TA is governed by the FInancial Disclosure regulations and NSS are blatantly, no argument, illegal. That is why multiple regulators have focused on removing them in order to protect shareholders.
If a TA was able to identify NSS, it would at least be included in annual audits of transfer agents by various regulators. However, any illegal activity is required to be reported immediately and potentially put client account on notice subject to cancelation
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