More than 50 Democratic lawmakers are demanding that Attorney General Jeff Sessions explain his decision to withhold “critical violence prevention funds” from sanctuary cities that refuse to cooperate with federal officials on immigration.

The letter, sent late Thursday and signed by 12 Senate Democrats and 41 House Democrats, asked how Sessions has the statutory authority to withhold Edward Byrne Memorial Justice Assistance Grant (JAG) program grants from cities that do not adhere to his latest conditions regarding federal immigration law.