The usual:
 
"Trevor Morrison, a constitutional law professor at Columbia University School of Law, suggested that Thomas may have been seeking an end to the matter.

"My guess would be that Thomas referred the case to the conference so that the full Court can deny it. If Thomas denied the application on his own, then Donofrio would be free to go to the other justices for their consideration,” Morrison said.

“This way,” the law professor continued, “the matter would be done with. Applications of this sort are hardly ever granted."
 
And:
 
"Audrey Singer, a senior fellow at Washington’s Brookings Institution, who is an expert on immigration, said that the Donofrio matter is “going nowhere.”

“There is no way that anyone can argue about whether Barack Obama is a citizen,” Singer said. “In this country, we have a system known as jus soli or birthright by citizenship. You are a citizen by being born on American soil and he (Obama) was born in Hawaii.”

Singer said that Donofrio’s argument that Obama’s father was a Kenyan national does not matter because citizenship is not based on parentage, but on where someone was born.  “This is the issue that some people have with illegal aliens in our country,” she said. “Children of illegal aliens, if they are born in the United States, are U.S. citizens. That is in the U.S. Constitution.”

https://www.afro.com/tabid/456/itemid/2273/Thomas-breaks-custom-forces-court-to-look-at-Obam.aspx