Note the linked EveryCRSReport page does not say that naked short selling remains legal, it merely says that it may not be fraudulent or abusive.
However, not all "naked" short selling violates SEC rules or is illegal or deceptive. In particular "market makers" are permitted to take actions that would not be allowed to others. Beyond that, if the seller is in fact able to "cover" the short sale, and was not deceptive, there may be no violation.
So let us look at a more official source. "Key Points About Regulation SHO" is an official DEC page on the regulation, It explains the history of the regulation, and summarizes the specific rules that make up Regulation SHO.
The page reads:
Although the vast majority of short sales are legal, abusive short sale practices are illegal. For example, it is prohibited for any person to engage in a series of transactions in order to create actual or apparent active trading in a security or to depress the price of a security for the purpose of inducing the purchase or sale of the security by others. Thus, short sales effected to manipulate the price of a stock are prohibited.
“Naked” short selling is not necessarily a violation of the federal securities laws or the Commission’s rules. Indeed, in certain circumstances, “naked” short selling contributes to market liquidity. For example, broker-dealers that make a market in a security generally stand ready to buy and sell the security on a regular and continuous basis at a publicly quoted price, even when there are no other buyers or sellers. Thus, market makers must sell a security to a buyer even when there are temporary shortages of that security available in the market. (citation omitted)
Rule 203(b)(1) and (2) – Locate Requirement. Regulation SHO requires a broker-dealer to have reasonable grounds to believe that the security can be borrowed so that it can be delivered on the date delivery is due before effecting a short sale order in any equity security. ...(citation omitted)
Rule 204 – Close-out Requirement. Rule 204 requires brokers and dealers that are participants of a registered clearing agency to take action to close out failure to deliver positions. Closing out requires the broker or dealer to purchase or borrow securities of like kind and quantity. ... If a participant has a failure to deliver that the participant can demonstrate on its books and records resulted from a long sale, or that is attributable to bona fide market making activities, the participant must close out the failure to deliver by no later than the beginning of regular trading hours on the third consecutive settlement day following the settlement date, referred to as T+6. ... Rule 203(b)(3) of Regulation SHO requires that participants of a registered clearing agency must immediately purchase shares to close out failures to deliver in securities with large and persistent failures to deliver, referred to as “threshold securities,” if the failures to deliver persist for 13 consecutive settlement days
- Selling stock short without having located stock for delivery at settlement. This activity would violate Regulation SHO, except for short sales by market makers engaged in bona fide market making. Market makers engaged in bona fide market making do not have to locate stock before selling short, because they need to be able to provide liquidity. However, market makers are not excepted from Regulation SHO’s close-out and pre-borrow requirements.
- Selling stock short and failing to deliver shares at the time of settlement. Rule 204 requires firms that clear and settle trades to deliver securities to a registered clearing agency for clearance and settlement on a long or short sale in any equity security by the settlement date or to take action to close out failures to deliver by borrowing or purchasing securities of like kind and quantity ...
- Selling stock short without having located stock for delivery at settlement and failing to deliver shares at the time of settlement. This activity may violate Regulation SHO’s locate and close-out requirements, as explained above. In addition, in fall 2008 the Commission adopted Rule 10b-21, referred to as the “naked” short selling antifraud rule. Those who deceive about their intention or ability to deliver securities in time for settlement are committing fraud, in violation of Rule 10b-21, when they fail to deliver securities by the settlement date.
- Selling stock short and failing to deliver shares at the time of settlement with the purpose of driving down the security’s price. This manipulative activity, in general, would violate various securities laws, including Rule 10b-5 under the Exchange Act.