So says Fox News Channel Legal Analyst, and former Judge, Andrew Napolitano:

Civil liberties attorney Harvey Silvergate agrees:

Under well-established First Amendment jurisprudence, what Gates said to Crowley–even assuming the worst–is fully constitutionally protected. After all, even “offensive” speech is covered by the First Amendment’s very broad umbrella (…) Today, the law recognizes only four exceptions to the First Amendment’s protection for free speech: (1) speech posing the “clear and present danger” of imminent violence or lawless action posited by Holmes, (2) disclosures threatening “national security,” (3) “obscenity” and (4) so-called “fighting words” that would provoke a reasonable person to an imminent, violent response.

As Silvergate goes on to discuss in an article well-worth reading, none of these four exceptions can reasonably be said to have applied to the confrontation between Crowley and Gates. Additionally, as Jacob Sullum notes, neither would Massachusetts state law on disorderly conduct justify the arrest in this case:

In Massachusetts, as in many states, the definition of disorderly conduct is drawn from the American Law Institute’s Model Penal Code. A person is considered disorderly if he “engages in fighting or threatening, violent or tumultuous behavior…with purpose to cause public inconvenience, annoyance or alarm” or “recklessly creates a risk thereof.” Crowley claims Gates recklessly created public alarm by haranguing him from the porch of his house, attracting a small crowd that included “at least seven unidentified passers-by” as well as several police officers. Yet it was Crowley who suggested that Gates follow him outside, thereby setting him up for the disorderly conduct charge. It’s hard to escape the conclusion that Crowley was angered and embarrassed by Gates’ “outburst” and therefore sought to create a pretext for arresting him. “When he has the uniform on,” Crowley’s wife later told The New York Times, “Jim has an expectation of deference.” As the Massachusetts Appeals Court has noted, “the theory behind criminalizing disorderly conduct rests on the tendency of the actor’s conduct to provoke violence in others.” Yet police officers often seem to think the purpose of such laws is to punish people for talking back to cops.

And yet, that’s not what the law says, as Massachusetts’ highest Court has recognized:

The officers’ presence, alone, did not suffice to prove the public element, regardless of any concern they may have felt as they witnessed the defendant’s confrontation with Sergeant Boss. As recognized in the commentaries to the Model Penal Code, behavior that has an impact only upon members of the police force is significantly different from that affecting other citizens in at least two respects: it is an unfortunate but inherent part of a police officer’s job to be in the presence of distraught individuals; and, to the extent that the theory behind criminalizing disorderly conduct rests on the tendency of the actor’s conduct to provoke violence in others, “one must suppose that [police officers], employed and trained to maintain order, would be least likely to be provoked to disorderly responses.” Model Penal Code § 250.2 comment 7, at 350. Accordingly, police presence in and of itself does not turn an otherwise purely private outburst into disorderly conduct.(9)

In other words, the mere act of talking back to a cop does not constitute a crime and should not justify arrest.

Gates was a hothead, but Crowley stepped outside the bounds of his Constitutionally-limited authority.