<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Technically when you are going through US INS and customs you are on US "soil" just the same as a US (or other foreign) consulate or embassy is foreign soil.</font>
This statement is not true. PFI is just part of Canada where the US agents have some special powers (until the last couple of years, they weren't allowed to carry guns, for instance).
Even embassies are not on foreign soil, as I recall the last time this was discussed here, our resident expert clarified that this only happened in 1944 when the Dutch queen gave birth in Ottawa, and that floor of the hospital was declared foreign soil.
andrew