Government would probably not be able to hack bitcoin if the owners uses airtight cold storage and choose a hosting provider that is trustable and a team of trustable employees. Most of the time, it's the inside job, not a actual security vulnerabilities.
Bitcoin cannot be 'hacked' but if there's malware on their computers once they transfer the coins from cold storage to their computers they could theoretically nab them.
You can get malware by installation of suspicious programs and lesser chance by a vulnerability if you keep it updated well. That would be a hot wallet hack which shouldn't happen anyway if proper security techniques are practiced. Large withdrawal should be processed manually and the hot wallet should contain a very small percentage of the total funds.