Child Trafficking Victims Protection and Welfare Act This bill provides for protections for children detained by the Department of Homeland Security (DHS). DHS shall develop guidelines for the treatment of children (under age 18 with no permanent immigration status) in U.S. Customs and Border Protection (CBP) custody. DHS must provide resources to address the needs of such children, including child welfare professionals, at each port of entry and Border Patrol station. The bill imposes various duties on such child welfare professionals, including the duty to report allegations of abuse. DHS may not remove a child from a parent or legal guardian solely for the purpose of deterring individuals from migrating to the United States or for promoting compliance with the immigration laws. DHS must (1) assign a family unit tracking number to each family member apprehended at the border, (2) allow humanitarian organizations and state and local child welfare agencies to monitor children in detention and conduct unannounced inspections, (3) promulgate regulations establishing basic standards of care for children in short-term CBP custody, (4) ensure that children apprehended by CBP receive an interview and screening with a child welfare professional and are provided information about their rights, and (5) provide each apprehended parent or legal guardian and each child with access to legal counsel. The U.S. Agency for International Development shall establish programs to support the safe and sustainable repatriation of an unaccompanied alien child to the child's country of nationality or last habitual residence.