ALBANY, N.Y. (AP) — A federal judge has ruled that wildlife protection and conservation groups can join New York state's effort to uphold its ivory ban being challenged in a lawsuit filed by antiques dealers.

A U.S. District Court judge in Manhattan on Monday granted a motion by the Natural Resources Defense Council and three other organizations to join the state in defending its 2014 law strictly limiting the sale of ivory and rhino horns.

Two art trade organizations have sued state Department of Environmental Conservation Commissioner Basil Seggos. The groups want the ban overturned, claiming it creates legal conflicts with existing federal laws restricting ivory sales.

The trade groups are opposed to hunting for ivory, but say sales of ivory antiques more than 100 years old should be allowed in New York.