The motion is here. An excerpt:
[T]he State of Texas and 37 other States … request that the Court divide oral argument for Petitioners, and allow Greg Abbott, Attorney General of Texas, on behalf of the amici States, 10 minutes of argument time. Petitioners support this motion, and have agreed to cede 10 minutes to the amici States….
[B]ecause they are sovereign governmental bodies, with strong interests in preventing crime and in maintaining their extant regulations on firearms, the amici States represent interests unique from those of Petitioners. And the amici States are well positioned to address any federalism concerns regarding the application of the Second Amendment to state and local governments…. [T]he amici States firmly believe that the incorporation of the Second Amendment presents no [federalism] concerns. Denying local governments the power to nullify the Amendment will not increase federal power, mandate any state action pursuant to federal directives, or preclude reasonable state and local regulation of firearms. It will simply prevent local governments, like the federal government, from abrogating the fundamental, individual right to keep and bear arms.
The states’ amicus brief is here. The states that haven’t joined are California (even though it endorsed incorporation in an amicus brief filed at the certiorari petition stage), Connecticut, Delaware, Hawaii, Illinois, Iowa, Maryland, Massachusetts, New Jersey, New York, Oregon, and Vermont. (All the non-signing attorneys general except the Hawaii AG are Democrats, though 21 of the 32 Democratic attorneys general did sign.)