Gamestop, Wall Street, and Halacha

The GameStonk Saga, as told by Wikipedia on 2/7/2021 and lightly edited by David Zakar:

The subreddit r/wallstreetbets (WSB) is an online community on Reddit, a social news website. The community is known for discussion around high-risk stock transactions. On January 22, 2021, approximately 140 percent of GameStop's public float had been sold short, meaning some shorted shares had been re-lent and shorted again. Observers on WSB believed the company was being significantly undervalued, and with such a large amount of the shares being short they could trigger a short squeeze, by driving up the price to the point where short sellers had to capitulate and cover their positions at large losses.
In January 2021, Reddit users on WSB built the foundations for a short squeeze on GameStop, pushing up the stock price significantly. The stock price increased 1,500 percent by January 27 over the course of two weeks, and its high volatility caused trading to be halted multiple times. According to Dow Jones market data, more than 175 million shares of GameStop were traded on January 25, the second largest total in a single day, surpassing its 30-day average volume of 29.8 million shares. Some of those investing into the stock were young teenage investors.
After GameStop's stock closed up 92.7 percent on January 26, business magnate Elon Musk tweeted "Gamestonk!!" along with a link to WSB. A brief, sharp rise in the share price to over $200 followed Musk's tweet. As of January 28, 2021, the all-time highest intraday stock price for GameStop was $483.00 (nearly 190 times the low of $2.57 reached 9 months earlier in April 2020). In pre-market trading hours the same day, it briefly hit over $500, up from $17.25 at the start of the month.
On January 28, Robinhood halted purchases of GameStop, AMC Theatres, BlackBerry Limited, Nokia Corporation, and other volatile stocks from its trading platform; customers could no longer open new positions in the stock, although they could still close them. Other brokerages soon followed suit. Many traders were furious, and called for class-action lawsuits in multiple popular Reddit posts. Some users alleged that Robinhood was selling shares without consent; Robinhood denied these allegations.
Several brokerage firms, including Robinhood, stated on January 29 that the restrictions were the result of clearing houses raising the required collateral for executing trades. On January 29, it was reported that Robinhood had raised an additional $1 billion to protect the company from the financial pressure placed by the increased interest in particular stocks and meet the collateral requirements of clearing houses. On January 31, Robinhood announced it had removed several of these restrictions and would only limit the sale of eight securities.
On February 1 and 2, the stock price for GameStop declined substantially, losing more than 80 percent of its value from its intraday peak price, recorded during the previous week. GameStop shares lost 60 percent of their value on February 2, closing below $100 for the first time in a week. Reports estimated that about $27 billion in value had been erased. CNN reported that the drop was partly due to restrictions imposed by Robinhood and other brokers on the number of shares that could be purchased at once by their clients. [DMZ - GME is now done to $51 on 2/11.]
Despite the decline, some r/wallstreetbets users rallied to convince other users to hold on to the shares, arguing either that they would increase in value or that such an action would send a political message.

Naked short selling is like conducting business for one's own benefit without gaining authorization to do so. We rule like R' Yosei; you cannot do business with someone else's property. The renter functions as an agent of the owner. Naked shorting is taking someone else's property without permission (ie, there is no actual stock to even be borrowed), and is thus prohibited. (paraphrase, Short Selling and Jewish Law, R' Dr. Aaron Levine, JSTOR).