October 16, 2000 —
The indictment or criminal prosecution of a sitting President would unconstitutionally undermine the capacity of the executive branch to perform its constitutionally assigned functions
Memorandum Opinion for the Attorney General
In 1973, the Department concluded that the indictment or criminal prosecution of a sitting President would impermissibly undermine the capacity of the executive branch to perform its constitutionally assigned functions. We have been asked
to summarize and review the analysis provided in support of that conclusion, and to consider whether any subsequent developments in the law lead us today to reconsider and modify or disavow that determination. We believe that the conclusion reached by the Department in 1973 still represents the best interpretation of the Constitution.
(39 pages, pdf file)

Source – Justice.gov