New York election law dictates any person who “[s]hows his ballot after it is prepared for voting, to any person so as to reveal the contents … is guilty of a misdemeanor,” according to a BuzzFeed report.
There have been legal challenges nationwide against ballot selfie bans on First Amendment grounds, including an unsuccessful one in New York this year. Eighteen states still explicitly ban the practice, according to the New York Times.
Trump has since deleted the tweet.
It's not the first time he's messed up voting for his father this year, either.
Both Eric Trump and his sister, Ivanka, missed New York's (egregiously early) deadline for switching their party affiliations to Republican, making them ineligible to participate in New York's closed GOP primary.
"They were unaware of the rules," Donald Trump told Fox News at the time. "They feel very, very guilty."
"But it’s fine. I mean, I understand that," he added.