Fearful that a decades-old court order blocking the Republican Party from engaging in certain Election Day activities could be extended for many more years, the RNC is warning its members not to engage in poll watching or any other so-called “ballot security” measures.

The RNC’s concerns are heightened because of the vigilante poll watching GOP nominee Donald Trump has been calling for from the stump.

A lawyer for the Republican National Committee sent a letter on the issue Wednesday to RNC members, the Wall Street Journal reported. The letter cites a 1982 consent decree the RNC agreed to after Democrats sued it for activities at polling places that they said were aimed at suppressing the minority vote.

The letter, sent to members from RNC general counsel John Ryder, said that he wanted “remind you of the restrictions placed on the RNC by the consent decree,” according to the Wall Street Journal.

Per the Journal:

Mr. Ryder said the settlement prevented the members acting in their capacity as national party officials from poll watching, recruiting or training poll watchers, making contact with voters at the polls, and a wide variety of other Election Day activities.

“You are encouraged not to engage in ‘ballot security’ activities even in your personal, state party or campaign capacity. If you elect to do so, please be aware that the RNC in no way sanctions your activity,” Ryder said in the letter, according to the report.

Democrats brought the lawsuit after the 1981 New Jersey gubernatorial election, when they said Republicans deployed off-duty cops to patrol around polling places in minority neighborhoods and engaged in a mailing campaign targeting black and Hispanic voters. According to the lawsuit, minority voters who did not return the mailer sent by the GOP were then put on a list the Republican poll watchers used to challenge their presence on the voter rolls.

The RNC agreed to “refrain from undertaking any ballot security activities … directed toward districts that have a substantial proportion of racial or ethnic minority populations,” according to the decree, though it is interpreted to allow Republicans to participate in more general poll watching activities.

The letter comes as Trump has amped up his rhetoric about a “rigged election” and urged his supporters to go monitor the polls themselves. At a rally in rural Pennsylvania, for instance, he told attendees that they “gotta watch the polling booths” because of the “stories” has heard about “certain areas.”

Republicans have sought, unsuccessfully, to get the consent decree lifted. It is set to expire next year, the Wall Street Journal said, but if a violation is found, the RNC risks having it extended through 2025.

“I ask your full cooperation in making sure that it is not extended,” Ryder’s letter said, according to the Journal.