Question:
What type of Demand will prevent an international application designating the U.S. to enter the national stage via the U.S. Designated Office?
Answer:
An international application designating the U.S. will enter the national stage via the U.S. Designated Office unless a Demand electing the U.S. is filed under PCT Article 31 whereupon entry will be via the U.S. Elected Office.
When entering the U.S. national stage following either Chapter I or Chapter II, the applicant has the right to amend the application within the time limit of one month from commencement.
Chapter Details:
The answer to this question can be found in chapter 1800 of the MPEP. This chapter covers Patent Cooperation Treaty.
The answer is from the 9th Edition, Revision 07.2022, Published February 2023. Depending on future changes to the MPEP, the question and answer may or may not be applicable in later Editions or revisions.
Section Summary:
This question and answer comes from section 1893.01(a) of the MPEP.  The following is a brief summary of section 1893.01(a).
1893.01(a) Entry via the U.S. Designated or Elected Office
An international application designating the U.S. will enter the national stage via the U.S. Designated Office unless a Demand electing the U.S. is filed under PCT Article 31 whereupon entry will be via the U.S. Elected Office.