California's top lawyer, Attorney General Xavier Becerra, said Monday that the Trump administration's request to add a citizenship question to the 2020 census is "illegal."

"The Constitution requires that, every 10 years, we accurately count every person in our country, regardless of citizenship status," said Becerra in a prepared statement.

Becerra joined 18 other state attorney generals Monday in sending an opposition letter to the federal government over the proposed citizenship question.