All government tenants are now able to sign-up into the Worldwide Microsoft Store for Business and are no longer blocked. At signup, you will be required to accept a Terms of Usage [TOU] like all other tenants joining the store before you can proceed.
For Government customers: The Store’s Shop setting is turned off by default and the Store Admin can enable this if desired. The Shop setting allows customers to turn shopping off (no shopping allowed).
To enable shopping, log into the Store with an Admin account, click Manage > Settings > Shop. From there you can enable shopping for your users.
More documentation and communication to follow.