Gov. Janet Mills speaks at an event in the Hall of Flag at the State House in Augusta in this file photo.

AUGUSTA, Maine — Maine’s Democratic governor has signed what supporters call one of the strictest online privacy proposals in the country.

The bill, signed by Gov. Janet Mills on Thursday, prohibits internet service providers from using, disclosing, selling or permitting access to a customer’s personal information unless a customer “opts in.” The bill only applies to providers operating within the state when providing broadband internet to customers physically located in the state.

[Subscribe to our free morning newsletter and get the latest headlines in your inbox]

It also requires providers to take reasonable measures to protect customers’ personal information from unauthorized use, disclosure, sale or access. And it prohibits providers from refusing to serve customers or charge customers who do not consent to their personal information being shared.

The Maine State Chamber of Commerce had called it bad policy to pass such restrictions on a state-by-state basis.