[Code of Federal Regulations]
[Title 8, Volume 1]
[Revised as of January 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 8CFR214.6]
Sec. 214.6 Canadian and Mexican citizens seeking temporary entry to engage in business activities at a professional level.
(a) General. Under section 214(e) of the Act, a citizen of Canada or Mexico who seeks temporary entry as a business person to engage in business activities at a professional level may be admitted to the United States in accordance with the North American Free Trade Agreement (NAFTA).
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Temporary entry, as defined in the NAFTA, means entry without the
intent to establish permanent residence. The alien must satisfy the
inspecting immigration officer that the proposed stay is temporary. A
temporary period has a reasonable, finite end that does not equate to
permanent residence. In order to establish that the alien's entry will
be temporary, the alien must demonstrate to the satisfaction of the
inspecting immigration officer that his or her work assignment in the
United States will end at a predictable time and that he or she will
depart upon completion of the assignment.
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Looking up at the Inspector's Field Manual you find:
“At the time application for admission, the citizen of Canada or Mexico will be subject to inspection to determine the applicability of section 214(b) of the Act (presumption of immigrant intent) to the applicant.”
Also
“However, section 214(b) of the Act is applicable to citizens of Canada or Mexico who seek an extension of stay in TN status and applications for extension or readmission must be examined in light of this statutory provision.”
I think this topic has been discussed many times before on various websites. Section 214(b) does not dictate what constitute intent.
However, in light of the above it is probably difficult to argue that the entry was intended temporary when you file AOS 5 days later…
Again, the adjusting officer decided not to challenge your intent. Doesn’t mean they can’t or wont. But you are correct that there is no 90 day rule establishing intent.