While I'm not fully qualified to comment on this (I'm not a lawyer/have no formal experience with securities law), my understanding is that it would depend on if the trader in question is providing investment advice. The SEC seems to have no clear position on the legality of copy trading at the moment - some of our customers are building copy trading apps, and they all seem to be in agreement that regulatory uncertainty is just one of the risks of building that sort of product at the moment.

There is probably a reason eToro, the premier copy trader, only does crypto copy trading in the US. Just food for thought. Effectively managing others' money would effectively make the trade-makers RIAs

We spoke with some lawyers while building our social investing app to gain a clearer understanding of this. Like Tim said, we're not lawyers, but the ones we spoke to said that this is a major gray area.