Protest rights are protected under the First Amendment to the U.S. Constitution—under the umbrella of freedom of speech, assembly, and petitioning the government for redress of grievances. At the same time, there are limits to those rights. It's not always clear when you've crossed the line from passionate but lawful protesting to actions that can get you arrested, but knowing the basic guidelines should help you be prepared.
The most significant limit on your right to protest is in the language of the First Amendment, which prohibits government interference with the right to assemble "peaceably." The U.S. Supreme Court long ago recognized the government's right to stop demonstrations that present a "clear and present danger" of violence or another "immediate threat to public safety, peace, or order" (Cantwell v. Connecticut, 310 U.S. 296 (1940)).
Without this kind of immediate threat, courts have generally held that police don't have the right to clear out a political demonstration just because they fear possible disorder or because protesters are "raucous," make the cops or other people mad, or slow traffic. (See, for example, Cox v. Louisiana, 379 U.S. 536 (1965) and Jones v. Parmley, 465 F.3d 46 (2nd Cir. 2006).)
The upshot of these standards set out by the courts: Law enforcement may break up violent protests and arrest participants who engage in violence or property destruction. You shouldn't be arrested just because you were present at a demonstration where other people violated the law, unless you directly incited them to violence. Nor should officers arrest you simply for yelling or cursing at them. But if your words turn to actions that could be considered violent—even actions that aren't likely to cause real injury, like throwing water bottles at cops in full riot gear—you risk arrest.
However, it's important to point out that some states have enacted or are considering laws that change these standards and can subject protesters to arrest even if they weren't violent or didn't damage any property. (More on these laws below.)
Once police decide that a protest is violent or presents an immediate threat, they may declare that it's an unlawful assembly, issue an order to disperse, and arrest anyone who doesn't leave right away. But under many court decisions (as well as local laws), officers must first give clear warnings that people can hear, provide an unobstructed exit route, and allow enough time to leave. Without that kind of notice and opportunity to obey, criminal charges for unlawful assembly or disobeying an order to disperse might not stand.
The same might be true if you're arrested during a controversial police tactic known as "kettling," which involves corralling protesters—along with journalists and anyone who happens to be in the area—not allowing anyone to leave, and then arresting everyone inside the cordon.
You can be arrested for violating a curfew issued during ongoing protests. Courts generally allow curfews when an executive has declared an emergency, and the circumstances show that restrictions on protest rights are necessary to maintain order because of an immediate threat to life or property.
It's not as clear whether courts would find that protesters' rights are violated by the enforcement of some other types of emergency orders, such as no-protest or "free speech zones" (which ban protests in certain public spaces where people have traditionally exercised free-speech rights) or "keep moving" orders applied to peaceful protesters (see Abdullah v. County of St. Louis, 52 F.Supp.3d 936 (U.S.D.C. E.D. Mo. 2014)).
Generally, authorities may require advance permits for demonstrations that will block traffic on city streets or even sidewalks. However, there are usually exceptions for spontaneous protests in response to recent events. Generally, police shouldn't break up protests that are simply slowing traffic or inconveniencing drivers and pedestrians—but that might not be the case in states that have passed laws making it a crime to block traffic during a protest (as discussed above).
Absent a permit or exceptions, you could face arrest for obstructing traffic, disorderly conduct, or similar "catch-all" crimes that cover a wide range of conduct. Police typically arrest protesters who take over freeways and bridges.
As part of your First Amendment rights, you're generally entitled to take videos and photos of the police when they're performing their duties in public. You shouldn't have to stop recording, show officers what's on your device, or turn over your phone just because they don't like what you're doing.
However, you could be arrested if you're obstructing or otherwise interfering with an officer's ability to carry out law enforcement duties—so you should record from enough of a distance that you can't be accused of getting in the way. You should also be open about what you're doing, to avoid being charged under some state laws against wiretapping, electronic surveillance, or eavesdropping. (Learn more about other exceptions to your right to record law enforcement, as well as steps you can take to protect your electronic devices and avoid surveillance at protests.)
You may be arrested for trespassing if you're protesting on some types of government property (including military installations, prisons, and courthouses) or on private property without the owner's permission. But you generally are allowed to protest on some types of private property that have been opened to public use, including parks known as "privately owned public spaces."
When you're protesting in front of city hall, police stations, or other government buildings, you could face arrest if you're blocking access to those buildings.
You might also be arrested for protesting within a "buffer zone" meant to keep protesters a certain distance away from sensitive locations like healthcare facilities that provide abortions. The U.S. Supreme Court has allowed some buffer zone restrictions and struck others down (for example, see Hill v. Colorado, 530 U.S. 703 (2000) and McCullen v. Coakley, 573 U.S. 464 (2014)).
Activists have long called for the removal of Confederate statues, flags, and other monuments honoring America's racist past (and present). But if, like many protesters around the world in 2020, you decide to take matters into your own hands—by toppling or spray painting monuments—you risk criminal charges for vandalism or worse. Penalties depend on the law in your state and the extent of the damage.
Staying on the right side of the law at a protest doesn't guarantee that you won't get arrested. In fact, it's not uncommon for law enforcement to make mass arrests at large protests, even when they know criminal charges won't hold up. But whether you've actually committed a crime or not, you continue to have important constitutional rights, including the right to have a lawyer present when you're being questioned. Many civil rights advocates suggest that you have a lawyer's phone number with you when you go to a protest (maybe even written on your arm), so you have someone to call when you're allowed a phone call after an arrest.