It's not just Mexican cement giant Cemex that's refusing to bid on the Great Wall of Trump; many of the firms in the super-concentrated large-scale construction sector are signalling their unwillingness to participate in the wall's construction.

It's not just reputational concerns, either: there's also the risk that California Democrats will pass their proposed law excluding any contractor who participates in the wall from state contracting; not to mention a legislative proposal that would ban the state's pension plans from investing in any of the people who help build the wall.

There are smaller companies that might take the contracts, but the sector is one of the many that is super-concentrated and building thousand-mile-long walls is hard.

That sits well with California lawmakers, Lara said. The legislature will consider a bill that would require the teacher and public-employee retirement funds, which together manage more than $500 billion, to divest from companies that help build the wall. "This legislature has made it clear what our position is on the Trump policies," said Lorena Gonzalez Fletcher, a Democratic assemblywoman from Oceanside who co-sponsored the measure. "We have supermajorities in both houses that are committed to lead the resistance."

Trump's Wall Is 30 Feet of Scary Politics for Builders

[Thomas Black/Bloomberg]

(Image: Berlin – Checkpoint Charlie (1970), Roger W, CC-BY-SA)