The world has become accustomed to Donald Trump voicing his criticism of companies via Twitter . But yesterday, when he criticized Nordstrom for dropping his daughter Ivanka’s fashion line, he crossed a line.

He originally tweeted from his personal handle, @realDonalTrump. But then, he—or another White House employee—used the official @POTUS handle to retweet this comment. This may seem like a small distinction, but according to legal expert Kathleen Clark, it is not trivial: He was deliberately invoking the power of the government to benefit his daughter’s company.

It’s the difference between Donald Trump writing a note on a scrap of paper and writing a note on official White House stationary, or making a comment in the privacy of a dinner party and making a statement behind the White House podium. “This is about using government resources and government symbols,” Clark says.

While Congress is unlikely to call him out on this, the Nordstrom tweet could be used as part of a larger case about how Trump is abusing government power.

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[Photo: Flickr user Gage Skidmore]