Twelve law school professors urged members of the Senate Judiciary Committee yesterday to reject legislation that would declare that human life begins at the moment of conception on the grounds that it is an unconstitutional attempt to overturn the Supreme Court's 1973 abortion decision.

The professors made their views known in a letter sent to each member of the Judiciary Committee as the Senate nears its first consideration this year of the emotional abortion issue. A Judiciary Committee subcommittee has scheduled hearings Thursday and Friday on the so-called "human rights bill," which would make abortion the taking of a human life and thus a crime.

Anti-abortion organizations, which thus far have failed to win constitutional amendment to overturn the Supreme Court decision, are backing the legislation as an equally effective means to their goal of outlawing abortions. Their legislative count shows that they can't get the two-thirds majority needed for an amendment but that they can easily win the simple majority needed to pass the legislation.

In their letter, the law school professors argued that Congress does not have authority to overturn the court decision by enacting a law. The proposed legislation, they said, is "an attempt to exercise unconstitutional power and a dangerous circumvention of the avenues that the Constitution itself provides for reversing Supreme Court interpretations of the Constitution."

According to Laurence Tribe of the Harvard Law School, the signers included both supporters of the 1973 decision that voided most laws restricting abortion and legal critics of that decision.