I think it would be totally fair for Robinhood etc to up margin requirements or even drop leveraged instruments. But If the client has $X in their account and they want to buy $X worth of GME or whatever, I don't see how that's a risk to their broker?
Rather than risk losing a ton of money, market makers have told the discount brokers that they won't be opening any new orders. You can't force someone to make a market for you.
Also, restricting trades I do not think is good for the market. Eventually all will stabilize. With less trades this is less volume in the market (overall) and I'm what would come of this.
w.t.f?
So like the 2009 crash, let's see how to screw again the retail investors?