''The philosophy department also, as usual in the US, wanted to give me a small honorarium.''
A document on the US Department of State, Bureau of Consular Affairs website said no salary could be paid to lecturers or speakers, ''other than expenses incidental to the visit''.
''If an honorarium will be received, activities can last no longer than nine days at any single institution or organisation.''
Being within the law appeared not important when an officer working for the United States Department of Homeland Security ''snatched'' her passport, letters and boarding passes, she said.
What followed was a long wait where she said she had ''no idea'' why she was being detained, before eventually missing her flight and being told the reason for her non-admission was paid employment.
''I then pointed out according to the visa waiver programme that I was allowed to do lectures and receive honorariums at five universities over a six-month period.
''He flatly denied that was the case.''
Canadian immigration provided Prof Spencer with a contact for officials in America who encouraged her to book a new flight because she had been ''wrongly denied entry on a 'technicality'.''
However, by this time accommodation had been cancelled and a flight back to New Zealand booked.
''With no food all day, I was also in no mental state to make a decision,'' Prof Spencer said.
''Just holding back the tears was taking all my energy.''
She had received a verbal promise her future travel to the US would not to be put at risk by the incident, but she was yet to receive this assurance in writing.
US Embassy Wellington country public affairs officer Dolores Prin said the embassy could not discuss individual cases.
''In a situation where travellers are concerned by stories regarding other individuals' prior experiences, it may help to bring any documents supporting their status or travel.''
Prof Spencer said she was most concerned officials claimed she could not have expenses paid.
Given how often academics had expenses paid while attending conferences and symposiums the claim had ''serious consequences''.
She did not know when she would feel comfortable attempting to enter the country again.