registration block; blacklisting
Internet domain: blocking registration of domain names, email addresses, or accounts, often to prevent spam or abuse.
As a countermeasure against spam, we blocked registration from specific domains.
registration ban (soccer)
Sports domain: a ban on registering new players, typically imposed on a club as a penalty.
The club received a player registration ban due to financial violations.
Compound of 登録 (registration) and 禁止 (prohibition).