A better example is HMRC, the tax authority, in the UK. They won't tell you if your tax avoidance scheme is legal or not, but they will fine you or take you to court if they later decide it is not.
However:
> Even with a favorable ruling, a taxpayer has no absolute guarantee of the tax consequences, since the IRS can modify or revoke a previously issued private letter ruling if it is later determined that the ruling was incorrect or inconsistent with the current position of the IRS.
So even with a PLR, you have no guarantees.