Cipollone graduated from Covington Catholic High School in 1984.
He was a law clerk for Judge Danny Boggs of the United States Court of Appeals for the Sixth Circuit from 1991–1992, and served as an assistant to Attorney General William P. Barr from 1992–1993.
Here are some relevant excerpts, via The Federalist:
In the letter, authored by White House counsel Pat Cipollone, the Trump administration says Pelosi and other House Democrats are “seeking to overturn the results of the 2016 election.”
“You have denied the President the right to cross-examine witnesses, to call witnesses, to receive transcripts of testimony, to have access to evidence, to have counsel present, and many other basic rights guaranteed to all Americans,” Cipollone writes. “You have conducted your proceedings in secret. You have violated civil liberties and the separation of powers by threatening Executive Branch officials, claiming you will seek to punish those who exercise fundamental constitutional rights and prerogatives. All of this violates the Constitution, the rule of law, and every past precedent”.
￼“You have designed and implemented your inquiry in a manner that violates fundamental fairness and constitutionally mandated due process,” Cipollone wrote. “Your highly partisan and unconstitutional effort threatens grave and lasting damage to our democratic institutions, to our system of free elections, and to the American people.”
Here's a link to the WH site and the entire eight page letter in pdf format.
UPDATE: First some excerpts from the introductory paragraphs, before the legal arguments. Cipollone pitches it strong, no holds barred. The irresponsible assault on the Constitution is clearly set forth. I like--among other things--that Cipollone clearly presents Shifty Adam as the face of impeachment:
Many Democrats now apparently view impeachment not only as a means to undo the democratic results of the last election, but as a strategy to influence the next election, which is barely more than a year away. As one member of Congress explained, he is "concerned that ifwe don't impeach the President, he will get reelected."
President Trump took the unprecedented step of providing the public transparency by declassifying and releasing the record of his call with President Zelenskyy of Ukraine. The record clearly established that the call was completely appropriate and that there is no basis for your inquiry.
... information has recently come to light that the whistleblower had contact with Chairman Schiffs office before filing the complaint. His initial denial of such contact caused The Washington Post to conclude that Chairman Schiff "clearly made a statement that was false."
In any event, the American people understand that Chairman Schiff cannot covertly assist with the submission of a complaint, mislead the public about his involvement, read a counterfeit version of the call to the American people, and then pretend to sit in judgment as a neutral "investigator."
President Trump and his Administration reject your baseless, unconstitutional efforts to overturn the democratic process.
From the Conclusion:
For the foregoing reasons, the President cannot allow your constitutionally illegitimate proceedings to distract him and those in the Executive Branch from their work on behalf of the American people. The President has a country to lead. The American people elected him to do this job, and he remains focused on fulfilling his promises to the American people. He has important work that he must continue on their behalf, both at home and around the world, including continuing strong economic growth, extending historically low levels of unemployment, negotiating trade deals, fixing our broken immigration system, lowering prescription drug prices, and addressing mass shooting violence. We hope that, in light of the many deficiencies we have identified in your proceedings, you will abandon the current invalid efforts to pursue an impeachment inquiry and join the President in focusing on the many important goals that matter to the American people.