According to the US Department of Defense, the Veterans Benefits and Transition Act of 2018 allows military spouses to elect to file a state resident return using the military members state of legal residence. Before the Veterans Benefits and Transition Act, spouses could only claim the same state of residence if they and their service member were from the same state.
The benefit of this act is that military spouses will no longer need to file a separate resident return for their resident state. Instead they can file jointly with their spouse on the military member's state resident return.
For example, a Florida service member marries someone from North Carolina. When they move to Kentucky (due to military orders), the service member is able to continue claiming Florida residency under the Servicemembers Civil Relief Act, but the spouse's income would be taxable to the state of Kentucky, requiring the couple to file separate state returns. Under this new act, both are able to claim Florida as the state of legal residence.