Twenty Law professors have urged the Senate to reject President Nixon's nomination to the Supreme Court of William H. Rehnquist, assistant U.S. attorney general, in a letter mailed to 17 Senators on Monday.

The letter, published yesterday in the Congressional Record by Senator Birch Bayh (D-Ind.). maintains that Rehnquist is outside "the central stream of contemporary constitutional thought" on issues of individual liberty and civil rights.

The letter apparently influenced Senator Edward W. Brooke (R-Mass.) to announce his opposition to Rehnquist at a press conference yesterday. Roger Woodworth. Brooke's policy assistant, said last night that the letter had carried "extraordinary weight."

Louis L. Jaffe, Byrne Professor of Administrative Law, who signed the letter, said yesterday. "I think our letter will have some effect. One purpose of Bayh in releasing the letter was to affect Brooke and Brooke did come out today."

Laurence H. Tribe '62, professor of Law and another signatory of the letter, said that the opposition to Rehnquist was not based on his integrity, competence or political views, but on the extremity of his constitutional positions.

The professors said in the letter. "Our opposition to Mr. Rehnquist is based on our perception that his views on the relation between government and the individual...and in the area of human rights...place him outside the central stream."