You cannot wear a mask in public for the purpose of evading the police.

The Law Explained

Originally passed to combat the Ku Klux Klan and other anonymous vigilante groups, this statute makes it a crime to conceal your identity while in a public space to avoid the law. While medical masks are perfectly legal, wearing a disguise to hide from law enforcement adds extra charges to a suspect's rap sheet. It is a fascinating civil rights era law still used against modern criminals.