WASHINGTON — Law classmates of White House Counsel Pat Cipollone sent him a letter on Thursday, claiming his decision to block material and witnesses from the House impeachment inquiry "distorts the law and the Constitution," according to a copy of the letter obtained by NBC News.

"We are sorry to see how your letter to the congressional leadership flouts the traditions of rigor and intellectual honesty that we learned together," said the letter from members of the class of 1991 at the University of Chicago Law School.

Click here to read the letter

The letter was signed by 21 out of 32 alumni whose contact information was available to the solicitors, who estimated there were more than 160 students in their class. According to the text, the signers "hold a range of political views." The two alumni who began circulating the letter this week, Joshua Davis, an employment lawyer based in Boston, and Jeremy Feigelson, a cybersecurity and data privacy litigation lawyer based in New York, have both donated to Democratic campaigns. A review of public databases reveal at least three of the alumni who signed are Republican donors and others have not donated to either political party.

The House of Representatives, led by Democrats, has launched an impeachment inquiry into President Donald Trump after a whistle-blower complaint revealed a phone call he had in July with Ukrainian President Volodymyr Zelenskiy in which Trump appeared to be asking for dirt on one of his political opponents, Joe Biden.

As part of the inquiry, House committees have asked for internal documents from the White House.

On Tuesday, Cipollone sent an 8-page letter to Congressional Democrats, stating that Trump "cannot permit his administration to participate in this partisan inquiry under these circumstances." Cipollone's letter came hours after the White House blocked the testimony of Gordon Sondland, the U.S. ambassador to the European Union.

The University of Chicago Law School alumni said, "When any president openly invites the help of foreign powers for partisan political purposes, Congress in the exercise of its constitutional powers should conduct an inquiry and the White House should cooperate. Fair-minded lawyers can easily agree on this regardless of their politics. Your letter instead distorts the law and the Constitution for other purposes, including cable news consumption."