Person A establish a brokerage account with an online brokerage XYZ. He then gives person B authority to trade the account. The XYZ brokerage account gives person A and person B to different user names. Each user name access the account. Person B then uses person's A account to trade the account.
Did person B break the law? I was told by a broker that he did. It seems to me he did not.
The usual provisos about jurisdictional differences may apply, and the last sentence of the first paragraph currently uses "account" to relate to two different things - I'll assume that sentence means "Person B then uses person A's user information to trade the account".
It's clear that XYZ expected the two users of the account to use different user identifications - they issued two. An accusation of misrepresentation is most likely to come from the brokerage firm, though it could also come from an internal or external auditor or from A if A assumed that B knew that they were expected to use their own user identification.
There may be mitigation - if A said to B "Here's authority to use the account : these are my login details", and/or if XYZ did not effectively communicate the separate user details to B, a Reasonable Person could conclude that B had not knowingly misrepresented themselves as A.
As the question stands it looks like an accusation of misrepresentation against B would be both possible and reasonable.
