Niger’s military government has made a bold move by banning a well-known French aid organization, the Agency for Technical Cooperation and Development (Acted), from working in the country. This decision, announced by Niger’s Interior Ministry on Tuesday, comes as relations with France—its former colonial ruler—continue to deteriorate.

Acted, a Paris-based NGO, has been active in Niger since 2010. The organization has been helping locals, especially displaced communities, in a nation grap...