If it’s in the town/city then the local authority will require a planning submission. A ground survey will be required to ensure it doesn’t impact on any services…and some other details.
Highway / route… It’ll be a road authority school as BEAR that you’ll need to liaise with to ensure they just don’t remove it as a non-authorised sign.
Standard poles in town…. generally want the newer collapsing/shear type next to a high speed route.
In a field…see owner, less problematic that a .gov
Dave