They are not eligible for .eu anyway
Section 3.2 of EURid's Terms and Conditions of use of a .eu domain name state:
"To use the Domain Name in such a way that does not violate any third-party rights, applicable laws, or regulations, including discrimination on the basis of race, language, sex, religion, or political view;"
Leave.eu is run by a bunch of racists and they broke laws regarding the running of their leave campaign.
Section 3.3 states:
"Not to use the Domain Name (i) in bad faith or (ii) for any unlawful purpose."
The site is full of lies and misrepresentations.
Section 4.3: "the Domain Name registration is made in good faith, for a lawful purpose, and does not infringe the rights of any third party;"
Section 4.4: "the Domain Name is not contrary to public policy or morality (e.g. is not obscene or offensive), and is not unlawful;"
Plenty of grounds for their domain name being revoked.