He was remembered for being a "strong supporter of empirical work and interdisciplinary approaches to law" and "more concerned with the relation of legal education to the professor than any other member of the faculty".

[5] He was raised in Hyde Park and enrolled in the University of Chicago Laboratory Schools for primary and secondary education.

[2] Due to the close proximity of his home to the University of Chicago, he became acquainted with professors who inspired him to enter academia.

[7] After graduating from Cornell Law, Johnstone worked briefly in private practice before becoming an attorney in the Office of Price Administration.

[1] Having previously been stationed in Tanzania, he grew concerned that African legal education too closely mirrored the West and advocated for relinquishing control of the American-governed law school to native Ethiopians.

[11] Johnstone also aimed to train future students for government office at the university, replacing foreign professors on the faculty with Ethiopian ones.

[10] He chaired the Graduate Committee at Yale, efficiently managing a controversial program, and oversaw the school's admissions for a period.

[12] He was alone in teaching the specialty of property law, and made multiple unsuccessful efforts to increase the number of faculty in the field, though succeeded on only one occasion.

With no class rankings at the school, he remembered its absence as meaning "less push for top grades than there might be at other places".

His mastery of the intricacies of property law was treasured by generations of students, as were his insights into the legal profession.