Congress defines a security, and the SEC interprets the definition, and the courts subsequently interpret it if the SEC sues. Congress has made a definition tha

Congress defines a security, and the SEC interprets the definition, and the courts subsequently interpret it if the SEC sues. Congress has made a definition that does not apply to Bitcoin, and the SEC has interpreted the definition to not apply to Bitcoin. It hasn't come up in court, and it won't unless the SEC changes their minds first. But their arguments are sound and it's extremely unlikely that their interpretation could change, or that a court would agree with them if they did change. It's also unlikely that Congress would change the existing definition to apply to Bitcoin. It's much more likely that they would pass specific regulations for Bitcoin and cryptocurrency.