White House social media director Dan Scavino has been reprimanded for violating federal law when he used Twitter to call for the defeat of a Michigan congressman, according to a letter sent this week by the Office of Special Counsel.

“OSC has concluded that his activity violated the Hatch Act. Accordingly, we issued Mr. Scavino a warning letter. In addition, we note that Mr. Scavino was recently counseled about the Hatch Act by the Office of the White House Counsel,” Ana Galindo-Marrone, chief of the OSC Hatch Act Unit, wrote on June 5.

Scavino was advised by OSC that any future violation would be considered “a willful and knowing violation of the law,

The reprimand is a response to an ethics complaint filed by the liberal ethics watchdog Citizens for Responsibility & Ethics in Government (CREW) after Scavino and Rep. Justin Amash, R-Mich., tussled on Twitter.

The April 1 violation occurred in the middle of an intense debate over repealing ObamaCare that pitted the Trump administration against Amash and other members of the Freedom Caucus.

Scavino took on Amash on Twitter, tweeting that he was a “huge liability.”

Amash responded in kind.

“The rules are clear that government officials aren’t allowed to use their position for campaign activity,” said Noah Bookbinder, CREW’s executive director, in a statement released today.

“OSC has made clear with this ruling that they are going to enforce these important rules and work to keep the government free from inappropriate politics,” he added.

CREW also filed a complaint against Amash for using his Congressional account to respond to the Trump administration official. The OSC declined to comment on whether a decision has been reached in that case.

Serafin Gomez conributed to this report.