Same-sex marriage activists presented a giant wedding card for Prince William and Kate Middleton outside the gates of Buckingham Palace on April 25.
The card congratulated the royal couple on their wedding, which took place four days later, and urged them to support legalization of same-sex marriage. The United Kingdom currently offers same-sex couples civil partnerships that carry the same rights as marriage.
The card said: "We wish you a happy life together. You can get married, gay people can't. We are banned by law. We ask you to support marriage equality."
Organizer Peter Tatchell said the action was well-received.
"Everyone outside the palace expressed support for marriage equality. We didn't get a single negative reaction," he said. "We are urging the royal couple to find a way, within official protocol, to indicate their support for marriage equality."
Tatchell is involved in a case before the European Court of Human Rights that seeks to overturn Britain's ban on same-sex marriage and its ban on opposite-sex civil partnerships. The case, sponsored by the Equal Love campaign, was filed by four gay and four straight couples.