Lawyers for the BBC argued that Ivanka Trump, her husband Jared Kushner, and Donald Trump, Jr. have “personal knowledge” and likely have records relevant to elements of Trump’s claims against the broadcaster, according to a filing Friday in federal court in Florida.

The broadcaster has been unable to serve subpoenas because the three have Secret Service protection and other security personnel around them, the filing says.

Trump filed the lawsuit in December seeking $10 billion in damages from the BBC, accusing it of defamation and deceptive and unfair trade practices.

The filing says the BBC asked Trump to accept the subpoenas on his daughter and son-in-law’s behalf or to direct the Secret Service to allow the subpoenas to be served, but he refused. The broadcaster asked the court to allow the subpoenas to be served by email and certified mail.