There are two alternative bases for this rule. The only way a
nonresident debtor can be denied use of the federal
exemptions is if the applicable state has expressly opted out
for nonresidents. 11 USC § 522(b)(2). If there is no applicable
state, there can be no opt-out, and debtor retains use of the
federal exemptions.
In re Arispe, 289 B.R. 245 (Bankr.S.D.Fla.
In re Goldsmith, 2003 WL 295690 (Bankr.S.D.Fla.2003).

Second, the "savings clause" in 11 USC § 522(b), hanging
paragraph, (added by BAPCPA) states: “If the effect of the
domiciliary requirement under subparagraph (A) is to render
the debtor ineligible for any exemption, the debtor may elect to
exempt property that is specified under subsection (d).”