Final answer:
The organization that does not enforce MSRB rules is the Comptroller of the Currency.
Step-by-step explanation:
The MSRB (Municipal Securities Rulemaking Board) is the organization that enforces MSRB rules. The Comptroller of the Currency, FINRA (Financial Industry Regulatory Authority), and the SEC (Securities and Exchange Commission) all have different roles and responsibilities in the regulation of securities, but they do not specifically enforce MSRB rules.