Via Bacon's Rebellion, Paul Goldman has this column explaining how laws passed in a special session of the General Assembly (such as the recent tax bill) take effect, according to the Virginia Constitution, "on the first day of the fourth month following the month of adjournment of the special session." Va. Const., art. IV, section 13. The tax bill on its face takes effect August 1, the Constitution says it can't take effect (without emergency status) until September 1.