Only a day after Twitter revealed that it had received a summons from the Department of Homeland Security demanding identifying information about an anonymous anti-Trump user account (and only hours after the government abandoned its attempt), Senator Ron Wyden is telling the agency it needs to explain itself.

The letter, addressed to acting commissioner of U.S. Customs and Border Protection Kevin McAleenan, requests that the agency “conduct an internal review into why and how CBP issued the summons and report on the results of that review.”

“On its face,” the letter continues, “CBP’s request for information on the @ALT_USCIS Twitter account appeared completely unrelated to the authority cited for the summons. Even more concerning is the possibility that CBP requested this information to learn if the accountholder(s) are employed by the Department of Homeland Security in order to take retaliatory action or otherwise squelch the exercise of First Amendment right to comment on U.S. policy, and to make these comments anonymously.”

You can read the full letter below.