He received a Juris Doctor from Loyola Law School in Los Angeles in 1926.

[1] Yankwich tried Cain v. Universal Pictures (1942), a case in which the writer James M. Cain sued Universal Pictures, the scriptwriter and the director for copyright infringement in connection with the film When Tomorrow Comes.

Yankwich ruled that there was no resemblance between the scenes in the book and the film other than incidental scènes à faire, or natural similarities due to the situation, establishing an important legal precedent.

He invalidated segregation in Lopez v. Seccombe (1944), a decision prohibiting discrimination against persons of Mexican ancestry in San Bernardino's public recreational facilities.

Indeed, he testified that, in addition to this, he was led to believe that if he did not vote, he would lose his food ration card.