Final answer:
UNFETTERED DISCRETION in free speech regulation is an unconstitutional limitation that occurs when a law is so vague or grants arbitrary power that it chills or suppresses free speech.
Step-by-step explanation:
The limitation imposed on free speech regulation known as UNFETTERED DISCRETION refers to the principle that laws impacting freedom of speech cannot be so vague or provide such arbitrary power to decision-makers that they result in a detrimental effect on the exercise of free speech, referred to as a "chilling effect." A law that grants unfettered discretion would be unconstitutional because it could potentially inhibit individuals from expressing themselves freely out of fear of unknowingly violating the law.
Content neutrality is also a significant standard for evaluating free speech limitations, meaning the government cannot selectively restrict speech based on its subject matter. Additionally, the law must pursue its objective through the least drastic means and cannot include prior restraint, except under extreme circumstances. Lastly, speech that presents a clear and present danger may sometimes be unprotected, according to landmark precedents like Schenck v. United States.