Pence, the former governor of Indiana, chairs the voter fraud commission. It is unclear how he or the commission will respond to the states who are not giving the data freely.
Trump set up the commission through an executive order last month. He said it aims to “promote fair and honest” federal elections.
But critics have questioned the body’s intentions, arguing that it may seek to suppress voters. More than once, Trump has claimed without evidence that millions of people illegally voted against him last year.
“California’s participation would only serve to legitimize the false and already debunked claims of massive voter fraud made by the president, the vice president, and Mr. Kobach,” California secretary of state Alex Padilla said.
New York Gov. Andrew Cuomo also said he would not “perpetuate the myth voter fraud played a role in our election.”