Special Counsel Robert Mueller’s office is not staying silent following explosive accusations by a lawyer for President Donald Trump’s transition team that the investigators looking into claims of collusion with Moscow during the campaign unlawfully received tens of thousands of emails from the General Services Administration.

Kory Langhofer, the attorney for the Trump for America transition team, sent a seven-page letter to the Senate Homeland Security Committee and the House Oversight Committee, claiming that employees of the GSA “unlawfully produced TFA’s private materials, including privileged communications, to the special counsel’s office.” The GSA, which holds all the transition documents, handed over the requested “copies of the emails, laptops, cell phones, and other materials” of 13 members of the transition team even though the agency “did not own or control the records in question.” Langhofer claimed that they were never informed that the documents were handed over and there were potential violations of attorney-client privilege as well as the Fourth Amendment, which protects against unlawful search and seizure.

Axios, which broke the news of the emails, explains why the communications matter:

The transition emails are said to include sensitive exchanges on matters such as potential appointments, gossip about the views of particular senators involved in the confirmation process, speculation about vulnerabilities of Trump nominees, strategizing about press statements, and policy planning on everything from war to taxes.

A source tells Axios that the transition team will be sending a letter to Mueller asking for some emails to be returned because they’re privileged. “What they did is totally illegal, and they need to fix it,” the source said. But Mueller’s team begs to differ. “When we have obtained emails in the course of our ongoing criminal investigation, we have secured either the account owner’s consent or appropriate criminal process,” Mueller spokesman Peter Carr said.

Mueller’s spokesman isn’t the only one pushing back. GSA Deputy Counsel Lenny Loewentritt also contradicted the claims made by Trump’s transition team. Loewentritt specifically rejected a claim by the transition lawyer that the late GSA general counsel made a commitment to inform Trump’s team if there were specific requests for any documents because the campaign “owned and controlled” emails that were sent at the time. In an interview with BuzzFeed, Lowentritt said that the truth is the exact opposite because the transition team was clearly told that “in using our devices,” materials “would not be held back in any law enforcement” actions.

Former federal prosecutor Renato Mariotti took to Twitter to explain why Trump’s transition team is “playing politics” but the issue itself “is a bad sign for them.” For Mariotti, what is unusual in this case is that Mueller’s team got the emails from the GSA rather than the Trump transition. That suggest “Mueller was concerned that he wouldn’t receive all of the emails if he obtained them from the Trump team,” Mariotti writes. “That’s surprising and suggests that he has reason to distrust Trump’s team.” Besides Mariotti makes clear that “disputes over privilege are common when prosecutors obtain emails and documents from third parties.”

THREAD: Why are Trump’s lawyers upset that Mueller obtained transition emails from a government agency? (Hint: They’re just playing politics, but this is a bad sign for them.) — Renato Mariotti (@renato_mariotti) December 16, 2017

9/ One reason comes to mind. Mueller was concerned that he wouldn’t receive all of the emails if he obtained them from the Trump team. That’s surprising and suggests that he has reason to distrust Trump’s team. — Renato Mariotti (@renato_mariotti) December 16, 2017

The privilege claims though could have been easily resolved with a letter to Mueller rather than Congress, Mariotti writes, noting that’s the biggest hint that the ultimate goal is to taint the investigation. “The biggest conclusion I’d draw from their letter is that they’re concerned about Mueller’s investigation and are doing whatever they can to discredit it,” Mariotti writes. “Their claims themselves are weak and are meant to persuade people who know nothing about criminal investigations.”

19/ The biggest conclusion I’d draw from their letter is that they’re concerned about Mueller’s investigation and are doing whatever they can to discredit it. Their claims themselves are weak and are meant to persuade people who know nothing about criminal investigations. /end — Renato Mariotti (@renato_mariotti) December 16, 2017

Rep. Eric Swalwell also went on Twitter to dismiss the supposed complaints by the transition team as much ado about nothing. “‘Private documents’ on a U.S. Government, public email system? What are they afraid was found? Baloney. This is another attempt to discredit Mueller as his #TrumpRussia probe tightens,” he wrote on Twitter.

“Private documents” on a US Government, public email system? What are they afraid was found? Baloney. This is another attempt to discredit Mueller as his #TrumpRussia probe tightens. https://t.co/VZTkwiGmoB… https://t.co/q0HTbwpQRK — Rep. Eric Swalwell (@RepSwalwell) December 16, 2017