NEW YORK (AP) — Donald Trump says the federal judge presiding over a lawsuit brought by former Trump University students has an “absolute conflict” in handling the case because he is “of Mexican heritage.”

The presumptive Republican presidential nominee tells The Wall Street Journal that U.S. District Judge Gonzalo Curiel has “an inherent conflict of interest” because Trump is “building a wall,” a reference to Trump’s proposal to build a wall along the border between the U.S. and Mexico.

Trump has brought up Curiel’s ethnicity several times this year, including last week at a rally in San Diego.

Curiel was born in Indiana and served as a federal prosecutor and a judge in the California state judicial system before being nominated to the federal bench by President Barack Obama in 2011.