There are different layers here. Baked into the exchanges (NYSE, Nasdaq) are circuit breakers which halt all trading on certain volatility conditions. The inte

There are different layers here. Baked into the exchanges (NYSE, Nasdaq) are circuit breakers which halt all trading on certain volatility conditions. The intent is to stabilize prices. This is not what happened here. What happened here is a broker (Robinhood) decided to not accept certain kinds of orders. It wasn't a market shutdown, it was a specific manipulation to stop the purchase but _not_ the sale of an instrument, causing the price to drop.