Baggett v. Bullitt (1964) struck down a state law that mandated loyalty
oaths for state employees, thereby interfering with their First Amendment
rights of association.

Beilan v. Board of Education (1958) glossed over First Amendment concerns
and upheld a teacher’s dismissal for refusing to answer questions about
membership in a communist group.

Cole v. Richardson (1972) upheld a loyalty oath required for state
employees against a First Amendment challenge. The Court did not think the
oath was too vague.

Connell v. Higginbotham (1971) used the First Amendment to strike down a
loyalty oath that required teachers to affirm they did not believe in the
violent overthrow of government.

In June 1865, Missouri, whose citizens had been deeply split by the Civil War, adopted a constitution that barred from voting any individuals who were unwilling to take an oath that they had never aided the Confederacy or any of its participants or who had left the state to escape conscription.   They also would

Elfbrandt v. Russell (1966) said an Arizona statute requiring state
employees to sign a loyalty oath infringed on First Amendment freedom of
political association.

Nostrand v. Little (1960) looked at a state law that required public
employees to take loyalty oaths. The Court dismissed the First Amendment
questions raised by the case.

In Speiser v. Randall (1958), the Supreme Court ruled that the state cannot
condition the receipt of a tax exemption on a loyalty oath to not overthrow
the government.

Whitehill v. Elkins (1967) struck down a loyalty oath requirement at a
university after a teacher who had been offered a job challenged it on
First Amendment grounds.

In Wieman v. Updegraff (1952), the Court said a loyalty oath requirement
for Oklahoma state employees violated the First Amendment freedoms of
speech and association.