First, the family benefits from over $500 million in investments extended by a conglomerate owned by the Chinese government in an Indonesian development project that involves the Trump Organization, revealed just days before President Trump announced his decision to bail out ZTE. The developer described the Trumps as partners in the project. Because the president retains his financial interest in the Trump Organization, this investment directly benefits him.

But that is not all. While all of this was happening, the Chinese government also approved seven new trademarks for the business of Mr. Trump’s daughter Ivanka Trump. They come on top of others extended to her and her father’s enterprises since the 2016 election. The value of these trademarks to the Trumps is hard to quantify, but it could well be many millions of dollars. Moreover, we just learned that Ms. Trump and her husband, Jared Kushner, made $82 million last year. Because of shortcomings in the disclosure form, their exact financial dealings in China are hard to trace. But it is fair to say she has almost certainly benefited from her Chinese trademarks.

To China, $500 million here and a few trademarks there is not even a rounding error. But the possible consequences to the United States are extremely dangerous. That is why Mr. Trump’s Chinese and other foreign profiteering has been challenged in American courts. Last week, more than 200 members of the minority party in Congress sought standing in the Federal District Court in the District of Columbia for their case alleging that President Trump has violated the Constitution by accepting benefits (“emoluments”) from China and other foreign governments.

Standing has already been granted in a separate case brought by Maryland and the District of Columbia, and this week brought the latest hearing in that case, on the scope of the constitutional prohibition. A third lawsuit is on appeal in the Second Circuit Court of Appeals, in New York (one of the authors, Mr. Eisen, is co-counsel in these two cases).

Now a bipartisan group of Senate leaders have moved to reverse the ZTE deal. The Senate provision, introduced by the Republicans Tom Cotton and Marco Rubio and the Democrats Chris Van Hollen and Chuck Schumer, would put ZTE back on the sanctions list.

These senators, and their supporters, sound committed to their position, and it is unlikely the Democrats will back down. But now that Mr. Trump has returned to Washington, he is surely going to demand that the Senate drop it, whether because he’s “winning” on foreign policy and knows best what he’s doing with China, or on some other justification.

The Senate must hold firm and Congress must pass this amendment. Otherwise, it will not be long before we face a series of future transactions posing similar threats to our national security — and similar benefits to the Trumps.