The USCIS has released a Memorandum to Field Leadership the subject of which is: Supplemental Guidance Relating to Processing Forms I-140 Employment-Based Immigrant Petitions and I-129 H-1B Petitions, and Form I-485 Adjustment Applications Affected by the American Competitiveness in the Twenty-First Century Act of 2000 (AC21)(Public Law 106-313), as amended, and the American Competitiveness and Workforce Improvement Act of 1998 (ACWIA), Title IV of Div. C. of Public Law 105-277.
The subject is a mouthful and the memo is content-full and definitely worth reading.