The office said in a June 5 letter to watchdog group Citizens for Responsibility and Ethics in Washington (CREW), which filed a complaint about Scavino's tweet, that it will not punish him for it - but warned that any future violation would constitute a "willful and knowing violation of the law" and could bring legal repercussions.
Dan Scavino Jr., the White House's point man on social media, is in trouble because of, well, his social media.
The OSC determined that the tweet was posted "while invoking his official position at the White House" and therefore "this activity violated the Hatch Act".
In an April tweet, Dan Scavino - a longtime Trump employee considered within the president's inner circle - encouraged a primary challenge to Representative Justin Amash, a Michigan Republican who opposed the first version of legislation backed by the president to scale back Obamacare.
Amash was among the Freedom Caucus members who pushed back against the President, tweeting that Trump had surrendered to the Washington swamp he promised to fight.
Scavino is one of the president's most loyal and longest-serving aides in the White House.
"The rules are clear that government officials aren't allowed to use their position for campaign activity", CREW Executive Director Noah Bookbinder said in a statement Friday. On social media, that means no campaigning while on duty or while using a professional account. A review of his Twitter account did not find additional violations.
The office told Scavino any additional violations of the law could lead to further action, including losing his job.
CREW complained about the threat to the Office of Special Counsel (OSC), noting that Scavino's Twitter account showed him in the Oval Office next to the presidential flag and showed Trump at a lectern with the presidential seal.