California Gov. Gavin Newsom called for a national billionaires tax in an opinion piece published on Friday.

Newsom said he opposes a one-time state wealth tax.

“You may not be able to pick up and move to Texas or Florida to shelter your income from taxation, but I promise you that billionaires can, and do,” Newsom wrote. “Wealth is movable, and it shops for the state with the lowest taxes. The fight belongs at the federal level, where this broken system was created in the first place.”

Newsom has proposed a special minimum tax on individuals with a net worth above $100 million.