After three years practicing law, Bernstein left the legal profession to return to the study of history, doing graduate work at New York University.
From 1997 to 2004 Bernstein was co-editor of book reviews for H-LAW, the listserv co-sponsored by H-NET (Humanities and Social Sciences Network On-Line) and the American Society for Legal History.
In the fall semester of 2011, Bernstein joined the Skadden, Arps Honors Program in Legal Studies at the City College of New York as an adjunct professor of political science.
Beginning in the fall 2015 semester, he was named a full-time lecturer in law and political science teaching classes like "The Presidency".
In November 2002, in addition to his scholarly activities, Bernstein became director of online operations at Heights Books, Inc., a used-bookstore in Brooklyn.
Following Are We to Be a Nation?, Bernstein published Amending America: If We Love the Constitution So Much, Why Do We Keep Trying to Change It?, a history of the U.S. Constitution's amending process and the successful and unsuccessful attempts to amend the Constitution from 1789 through the early 1990s; Thomas Jefferson and Bolling v. Bolling: Law and the Legal Profession in Pre-Revolutionary America, coedited with Barbara Wilcie Kern and Bernard Schwartz (the full text, transcribed with scholarly annotations, of the pleadings and arguments of a complicated 1770 lawsuit about wills and bequests that pitted George Wythe against Thomas Jefferson);[5] and Thomas Jefferson, published in 2003.
Roots of the Republic: American Founding Documents Interpreted, coedited with Schechter and Donald S. Lutz of the University of Houston, also appeared in 1990.
In 2016 he published the edited volume An Expression of the American Mind: Selected Writings of Thomas Jefferson (Folio Society).