Here is the opinion in Navajo Nation v. Dept. of Interior:
The Navajo Nation delivered a proposed funding agreement to the Bureau of Indian Affairs, an agency within the United States Department of the Interior, during a partial government shutdown. By law, the BIA had 90 days after receipt to act on the proposal or it would be deemed approved. The BIA did not consider the proposal “received” until normal government operations later resumed, and issued a partial declination 90 days after that date. The Nation filed an action to enforce the proposal, contending that the BIA’s declination was untimely. The district court granted summary judgment to the DOI, holding that because the Nation had remained silent when the BIA indicated its position on the deadline, the Nation was equitably estopped from asserting an earlier one. The Nation brought the present appeal. We reverse the judgment.
Lower court materials here.