Mr. Saverin, a Brazilian-born immigrant to the United States, now lives in Singapore, which has no capital gains tax. He renounced his United States citizenship in September. With that act of antipatriotism, Mr. Saverin stands to avoid at least $67 million in United States taxes.

“Mr. Saverin has decided to ‘defriend’ the United States of America just to avoid paying his taxes. We aren’t going to let him get away with it so easily,” Mr. Schumer said. “It’s infuriating to see someone sell out the country that welcomed him and kept him safe, educated him and helped him become a billionaire.”