WASHINGTON -- Republican presidential nominee Donald Trump's call for election observers to prevent the Democrats from "rigging this election" could run afoul of a 30-year-old restriction on GOP activities targeting minority voters that stems from a New Jersey election.

The Republican National Committee and "its agents" have been under court-imposed limits since the 1981 New Jersey gubernatorial election, narrowly won by Tom Kean, in which the state party reportedly targeted heavily minority communities that tend to support Democratic candidates.

The question is whether Trump, who is raising money jointly with the RNC, could be considered an "agent" of the party.

"I think there's a good argument for that, but it is far from certain a court would agree," said election law expert Rick Hasen, a professor of law and political science at the University of California, Irvine.

Hasen first raised the issue in his blog.

On his campaign website, Trump asked supporters to "volunteer to be a Trump election observer" and "help me stop crooked Hillary from rigging this election."

"To be violating the injunction, the activity would have to be more than just election observation," Hasen said. "Depending on how it is done and how it is advertised, it could look more like intimidation."

The Republican National Committee has been under court-imposed limits since New Jersey's 1981 gubernatorial election.

During the campaign, state GOP officials sent letters to residents of communities with large numbers of black or Hispanic voters, and then challenged anyone whose mail was returned as undeliverable, even though they were working off outdated registration lists.

Voters in minority communities in the state were met at the polls by signs reading, "This area is being patrolled by the National Ballot Security Task Force," and by off-duty police officers and deputy sheriffs hired by the party who, according to the original complaint, "obstructed and interfered" with the normal operations of the polling places.

In response to a lawsuit brought by the Democratic National Committee and the state party, the RNC signed a consent degree in which it agreed to not undertake "ballot security activities" in areas with a large concentration of minority voters "where a purpose or significant effect of such activities is to deter qualified voters from voting."

Trump has raised the specter of the election being stolen because courts have thrown out voter-identification laws enacted by Republican-controlled state legislatures on the grounds that they discriminate against poor and minority voters who are more likely to support Democrats.

At a Trump rally last week in Altoona, Pa., Rep. Bill Shuster (R-Pa.), insinuated that the election would not be honest.

"The people of western and central Pennsylvania have to overcome what goes on in down in Philadelphia, the cheating, what they do," Shuster said.

Trump then echoed Shuster's sentiments.

"We have to be very, very careful," he said. "We're going to have tremendous voter turnout. We don't want to see people voting five times. I've heard some stories about certain parts of the state."

He asked his supporters to volunteer as poll watchers and he would have law enforcement officers in place.

"Without voter ID, there's no way you're going to be able to check it properly," Trump said.

Republicans have claimed such laws are needed to prevent in-person voter fraud, but a study by Justin Levitt, professor of law at Loyola Law School in Los Angeles, found just 31 possible cases out of more than 1 billion votes cast from 2000 through 2014.

One of those cases may have taken place in Hoboken in June 2007, when both city council candidates in a runoff election reported that people at the polls found someone else had voted in their names, Levitt said. It could not determined whether this was a case of actual voter fraud or simply a clerical error in which the registrar marked the wrong name.

"Requirements to show ID at the polls are designed for pretty much one thing: people showing up at the polls pretending to be somebody else in order to each cast one incremental fake ballot," Levitt wrote in the Washington Post "This is a slow, clunky way to steal an election. Which is why it rarely happens."

Party officials have attempted to get from under the constraints several times, but the courts have upheld the agreement, including the U.S. Supreme Court in 2013.

The agreement is due to expire in 2017 unless the Republicans are found to have violated its provisions, in which case the Democrats can seek to extend it.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant. Find NJ.com Politics on Facebook.