As tech companies fend off digital tax proposals from France and other countries looking to cash in on the success of American-grown firms, a new threat has emerged at home. A number of U.S. states, including Maryland, Nebraska and New York, have proposed their own taxes on the revenue or income companies generate from online advertising and other services.

The proposals vary in approach and scope, but they all center around the idea that big internet companies, having built their fortunes in part through the use of consumers’ personal information, should be contributing more to government coffers. The bills, which face mixed prospects for adoption, have drawn the ire of tech companies and other business groups, who say it could be challenging to determine precisely how much of their ad revenue comes from each state. In addition, tax experts said, the proposals could run afoul of federal law.