Finally, the risk might be greater still if Mr. Kushner negotiated such deals before Mr. Trump’s inauguration. That’s the possibility raised by Mr. Kushner’s pre-inauguration meetings with Russia. In December 2016, Mr. Kushner met with Sergey Gorkov, the head of a bank under American sanctions, Vnesheconombank. That meeting came after Mr. Kushner suggested a back channel of communications in a meeting with Russia’s ambassador, Sergey Kislyak, according to Mr. Kislyak.

Nor did Mr. Trump’s transition team alert the Obama administration before Crown Prince Mohammed bin Zayed al-Nahyan of Abu Dhabi in the United Arab Emirates visited New York in December 2016 for a meeting involving Mr. Kushner and others at Trump Tower.

While the proper authorities may not have been informed of this series of meetings, Michael Flynn, the former national security adviser who pleaded guilty and agreed to cooperate with Mr. Mueller’s investigators late last year, did attend or at least knew of them.