Buzz,
As a former Fed I was able and authorized to use them and I learned to like them.
Additionally, they are only controlled in the US and are widely available in most countries were I have worked.
As an FYI, the THV is also not covered under the destructive devices laws and AP ammo is not illegal to posess, the "Clinton law" (insert name of political mouthpiece) prohibited the manufacturer and importation of ammunition with a hardened core or a metallic projectile designed to be AP.
The THV is restricted from manufacture and importation under that law.
One other round that was actually more effective than the THV was the Mag Safe Fast Hardball round that also perforates soft body armor very effectively but gives much better soft tissue performance was also banned.
The MagSafe miniglock 9mm & 40 S&W loads in full size pistols and the SuperSwat .45 load also produce the same effects with greater wound ballistics and are cheaper than the THV.