In some countries there are additional local requirements to register a domain with that country's specific extension, such as to register a '.de' (Germany) and '.com.au' (Australia) domain. These can range from needing a local presence (i.e. the domain owner must be a citizen of that country) to requiring that the registering company is incorporated in the local country.
There are services that can assist you if you are looking to buy a website or domain that has an extension with these restrictions. An example is https://www.marcaria.com/ws/en/domains/worldwide-domain-registration and details of domains with additional requirements can also be found on this page.
(Please note this is just an example of such a service, Flippa cannot vouch for the services offered by this or other companies).
Please ensure that you review all additional requirements for the domain extension of the website or domain that you are looking to buy before you start bidding.