There are huge implications for employers—both civil and criminal

Management can spend up to six months in jail. Fines are $400 to $16,000 per employee depending on the circumstances.

Any criminal prosecution of the employers comes months/years after the employee detentions. (Typically need to establish the employer knowingly hired aliens without work authorization, and that requires more time/work.)

See the recent Asplund Tree service case where they agreed to pay settle for$95 Million to avoid jail.

The link has some recent stats on enforcement.

Link: https://immigrationview.foxrothschild.com/employment-verification-compliance-including-i-9s-e-verify-and-enforcement/employers-beware-ice-is-ramping-up-i-9-audits-to-record-levels/