In a report published Wednesday, the Human Rights Watch (HRW) pressure group said there has still been no justice for the deaths of 15 migrants in the waters off Ceuta last February.
"These were horrific deaths, and very serious allegations of wrongdoing by the Guardia Civil [Civil Guard]," HRW's senior Western Europe researcher Judith Sunderland said in the report.
Spain admitted that in last year's incident, its Civil Guard troops fired rubber bullets and teargas at the water while migrants were attempting to swim to Ceuta from neighboring Morocco.
Far from punishing those responsible for the migrants' deaths, Spain has recently said it will pass a law to legalize on-the-spot deportations at its borders.
The UN Refugee Agency (UNHCR) and other international organizations have condemned the move, stressing that migrants are fleeing conflicts and are persecuted in their home countries. The refugee agency has voiced concern about the rise in the Civil Guard's violence used to deter asylum-seekers.