"All documents and communications, from February 15, 2019 to present, relating to any communications by the President referring to the issuance of presidential pardons for potential violations of federal law relating to the enforcement of US immigration laws or the construction of a barrier along the US-Mexico border," the subpoena said on Wednesday.
McAleenan is ordered to testify before the Judiciary Committee on the morning of September 17, the subpoena said.
The subpoena said that it is requesting any legal opinion, guidance or memoranda relating to the issuance of pardons or legal obligations of Department of Homeland Security officials or employees on the border including the enforcement of US immigration laws or construction of the border wall.
The Trump administration has called for stricter immigration laws and policies for purposes of national security to prevent criminals and other maligned actors from pouring into the United States from Mexico.
The administration has earlier enforced several policies such as the "zero-tolerance" policy that separated illegal migrant families at the border - under which adults were prosecuted and held in federal jails, and the children placed under the supervision of the Health Department - the Remain in Mexico Plan, and most recently a new rule to end the Flores Settlement Agreement which prevents the US federal government from detaining migrant minors for more than 20 days.