Which of the following parties is permitted to purchase a security in an initial public offering (IPO)?

An RR's brother-in-law is considered a restricted person under SEC rules and is prohibited from purchasing securities in an IPO. This restriction is in place to prevent potential conflicts of interest and to ensure fair distribution of shares among qualified investors.

While an RR of a BD not involved in the underwriting may seem permissible, they are still generally classified as a restricted person. The SEC rules prevent registered representatives from participating in the purchase of IPOs to maintain the integrity of the offering process and avoid favoritism.

A BD that is not affiliated with the syndicate may have access to purchase shares; however, they are often still considered restricted if they have any affiliations with the underwriting process or their registered representatives. This limitation exists to prevent any unfair advantages during IPO allocations.