European Union regulators are investigating whether Network Solutions Inc., the dominant registrar of Internet addresses, is trying to bar rivals from the business of assigning addresses. Network Solutions soon will lose its 6-year-old monopoly for registering top Internet Web site addresses that end in .com, .org and .net. It also licenses other companies, including closely held Nominet UK, to register addresses such as country-specific ones that end in co.uk or org.uk. The EU is investigating whether Network Solutions is locking in current licensees such as Nominet to stop them from going to new rivals once the monopoly ends, said EU spokesman Stefan Rating. EU regulators are urging Network Solutions to scrap binding agreements as it begins competition.