The withdrawal of troops from Vietnam started in July 1969. The last combat units left in November 1972. That process took nearly 3 1/2 years, and a great deal of the equipment was left behind, both because it would take too much additional time to repatriate it and because much of it was too beat up to be worth bringing back to the States. The last of the military advisers left, as required by the Paris peace accords, in March 1973. The Case-Church Amendment, which forbade further US involvement in Southeast Asia, was passed in June 1973, three months after that.

I have been unable to locate any record of a Congressional mandate that required US withdrawal from Vietnam, and I have some difficulty imagining President Nixon not vetoing one if it were presented to him. Nor can I find any record of an effort, successful or otherwise, to remove monies for the Vietnam War from the Federal budgets for the late 1960s and early 1970s. I'd appreciate any assistance, such as a legal citation or bill number and date, that would help in locating this data.