Federal Public Access Policies: An Overview | Copyright at Princeton

"Federal regulations grant the US government a license to funded research via 2 CFR 200.315(b) also known as the “Federal Purpose License.” While not every agency relies explicitly on this regulation, it underpins their right to require embargo-free access to your work. Regardless of any agreement made with a publisher or other entity, recipients of federal research funding must comply with agency public access policies, or risk ineligibility for future funding. 

Please include the “Statement for Manuscripts” for your funding agency at the time of submission to alert your publisher to this requirement. This page will be updated as agency policies are finalized...."