De Jonge v. Oregon was a landmark Supreme Court case decided in 1937 that addressed the rights of individuals to assemble peacefully and express their views without government interference. The ruling affirmed the importance of freedom of assembly as a fundamental civil liberty, stating that the government could not restrict peaceful gatherings based on the content of speech or beliefs being expressed. This case highlighted how states must adhere to federal constitutional protections, reinforcing the concept of incorporation of civil liberties against state laws.