It’s illegal to intimidate voters in America. But what counts as voter intimidation? It’s sometimes a know-it-when-you-see-it situation, which makes it complicated to enforce.

Myrna Pérez, the director of voting rights at the Brennan Center for Justice, said nuance is often required to determine what’s legal and what is not. Of course, nuance is often lacking in heated moments. “There is a difference in how things are described and experienced,” she said. “So much of this is happening quickly and in real-time and involving situations that are fluid.”

There are some things that laws and precedents have pretty clearly decided, meaning we can say they do or don’t count as voter intimidation. What is allowed is often clearer, so let’s start there with the rules and some real-world examples.

In most states, it is legal to:

Hold rallies outside a polling location: Even one that may make some voters feel uncomfortable, as long as you’re outside the legal buffer zone, which is usually 100 to 150 feet. But just because it’s legal doesn’t mean it won’t get a tsk-tsk from election officials. More than 300 supporters of President Trump gathering at a poll site on early voting day in California caused election officials there to publicly warn that voter intimidation wouldn’t be allowed.

Bring a gun to the polls: Only six states and D.C. ban guns at all polling locations, according to the Giffords Law Center to Prevent Gun Violence. Another four say you can bring a gun, but you can’t conceal your weapon; it has to be out in the open. In most states, traditional polling locations like schools are government property, and there are laws about bringing guns onto school property.

Recently, Michigan’s secretary of state, Jocelyn Benson (D), said she was banning guns from being openly carried in and around polling places, which spurred gun rights groups to sue her. A federal judge in Michigan sided with the gun rights groups.

Be loud and annoying while in line to vote, or drive by and be loud and annoying: Here are some examples from The Washington Post’s Joshua Partlow of behavior election officials may disapprove of but don’t necessarily have the means to police:

In Craven County, N.C., an election worker reported that a Trump supporter was “loudly exclaiming political statements” and played a Trump rally loudly on her phone within earshot of others lining up to vote.
At one polling place at a church in Hendersonville, Tenn., last week, a Trump supporter drove by repeatedly in a large truck-and-trailer rig with Trump flags and music blaring from speakers, “creating a lot of havoc,” said Lori Ashley, the administrator of elections for Sumner County. The Trump supporter was not within the 100-foot buffer around the voting site and was not violating any laws, Ashley said. "I just stopped him and I said, ‘Hey, it’d be better if you weren’t here,’ ” she recalled. “Legally, there’s nothing I could do about it.

Still, there’s a balance to strike between First Amendment rights and voting rights, reports The Post’s Abigail Hauslohner. And lawyers tell her that free speech rights win out in these situations because it’s often unclear whether the instigators want to actually stop people from voting or are just trying to express their political views.

In a number of states, it’s not legal to:

Just show up to watch the polls. Poll watchers have to be trained and certified with their local jurisdiction to be present. Also, a number of communities don’t allow people who live outside the county to be poll workers. Similarly, armed groups can’t show up to the polls to monitor them. So consider when Trump said this at the first debate: “I’m urging my supporters to go into the polls and watch very carefully because that’s what has to happen. I am urging them to do it.” If people were to take him seriously and just show up, they’d almost certainly be ask to leave. This is standard across the United States.

Secretly film people dropping off their ballots. As the Trump campaign did in Pennsylvania to try to show people dropping off more than one ballot. That prompted the state’s secretary of state to say they are in touch with law enforcement about it. “Voter intimidation is illegal under state and federal law, and videotaping you, taking pictures of you without your consent, is part of that,” Secretary of State Kathy Boockvar (D) said.

Hire private security to monitor the polls. In Minnesota, a private, out-of-state security firm said it was recruiting former U.S. military Special Operations personnel to monitor polls. “I want to make 100 percent clear if an individual were to do that, that would be highly improper, and they don’t have the basis to do that,” Pérez said of private citizens or companies deciding to watch polls, adding it’s illegal.

Minnesota’s attorney general took legal action against this security company, prompting a settlement where the firm agreed not to come to the state. The only exception to this would be if, say, a drop-off box is located in a government building that might otherwise be closed as people drop off their ballots. Then, perhaps a security guard or other law enforcement official might make sure the box doesn’t get vandalized.

The president can’t send troops or armed law enforcement to the polls. He hasn’t explicitly threatened to send troops, but he has said he might send sheriffs or law enforcement to guard against voter fraud. The president does not have the authority to do that; he doesn’t control state and local police. And it’s against federal law anyway.

In a memo about this, the Brennan Center says “the law is crystal clear: it is illegal to deploy federal troops or armed federal law enforcement officers to any polling place."

Send threatening emails to voters or make calls warning them of bad things to happen if they vote. A robocall in Michigan targeted Black communities in Detroit, warning them of debt collection and arrest if they voted by mail. Registered Democrats in Arizona and other states got emails threatening them against voting. (“You will vote for Trump on Election Day or we will come after you,” some said.) The U.S. government said Iran was behind those emails. All of that is illegal.

Have law enforcement stand near polling places or drop off boxes: America’s not too distant history is filled with politicians being accused of sending armed law enforcement to polls in Black communities. (The Republican National Committee has been banned from the 1980s until this election from most poll watching for this reason.) Many states have since regulated where officers can be. They can sometimes be at the polls. A sheriff’s office in Florida said it would put deputies outside some polling locations after reports of armed security guards patrolling one. In Pennsylvania, some election officials decided to allow sheriff’s deputies as a way to keep the peace amid heightened tensions.

But Pennsylvania is also one of the states with the strictest rules for on-duty officers, according to the Brennan Center. It’s a crime there and in California for them to show up to the polls without first being called. Other states also have laws trying to limit officers unless needed.

Wear campaign gear to go vote: It may violate electioneering laws about campaigning within a certain amount of feet of a polling location. “Different states have different policies regarding how much election gear you can wear when going into the polling places,” Pérez said, “and there’s definitely some legal limits.”