Homeland Security Secretary Kirstjen Nielsen has requested the deployment of civilian law enforcement officers from several other cabinet departments to the U.S.-Mexico border as early as next week, according to an internal memo obtained by POLITICO.

In what current and former U.S. officials said would be an unprecedented move, the officers — who in most cases have duties entirely unrelated to border security — would help border patrol agents repel what the memo calls “migrant caravans originating from Central America.”

The request suggests that personnel with such assignments as guarding diplomats, patrolling national parks, and protecting nuclear weapons might effectively “become Customs and Border Protection personnel,” as one former Justice Department official put it, with the power to arrest border-crossers.