system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How can the NYSE put a freeze on buying stocks but not on selling? Are there not 2 sides to every transaction?
gpt
The NYSE doesn't put holds on one side of the transaction - as you suspect, for every buyer you must also have a seller.  They do sometimes flip the 'circuit breakers' and stop _all_ trading for a few minutes (to give a cool down and help prevent panic behavior).

Individual brokerages or clearing houses, however, can stop processing orders for specific transactions.  In the case of Robinhood, they stopped allowing people to buy, but still allowed sales.  The main market still allowed buying, which is why the sale orders placed by RH could still be processed.