Q: How is the lead-ban enforced?

The lead-ban is enforced by the states through state or local plumbing codes, or such other means of enforcement as the State may determine appropriate (Safe Drinking Water Act §1417(b)(1))....

The lead-ban is enforced by the states through state or local plumbing codes, or such other means of enforcement as the State may determine appropriate (Safe Drinking Water Act §1417(b)(1)). States not enforcing these requirement are subject to EPA withholding up to  5 percent of federal funds available to the state for state program grants (Safe Drinking Water Act 1417(c)).