Kansas had a State law making
it a crime for a person or company to "coerce, require, demand, or
influence any person not to join a union."
The law was in response to
the fact that a lot of business owners were requiring a promise not the
join a union as a condition of employment.
Coppage broke the law and was
found guilty and ordered to pay a fine. He appealed.
The US Supreme Court
overturned the conviction and declared the law to be unconstitutional.
The US Supreme Court found
that the law violated the freedom of contract as protected by the Due Process
Clause of the 5th
Amendment and 14th Amendment.
The Court reasoned that in a
free society, people entering into contracts were free to bargain
whatever they wanted. Since the employee was always free to decline the
offer, the employer was within his rights to bargain for whatever
conditions of employment they could both agree to.
This case was a follow-up to Adair
v. United States (208 U.S. 161
(1908)), in which the Court had invalidated a similar Federal law.