So.
In order to redownload Warcraft 3 Reign of Chaos and The Frozen Throne, you are supposed to go to your account game list https://account.battle.net/games and click on the download link for an installer.
This installer forces Reforged to download.
This no longer happens.
Instead, the link takes you to a support article which offers alternate download links https://eu.battle.net/support/en/article/256212
These alternate download links tell you that you are installing Reign of Choas or The Frozen Throne.
They do not.
What you currently get, is the default Bnet installer whcih does not force the startup for Reforged to run the old version only version of the client.
Edit:
Thanks to the Wayback Machine, the old install link has been found.
If you are affected by the mismanagement that has lead to this situation, you can go to the official blizard link https://downloader.battle.net/download/getInstaller?os=win&installer=Warcraft-III-Setup.exe which will attempt to download the Installer that will force Reforged to install with the modern content locked.
You will still require a Bnet account with the original codes redeemed to play
4 Likes
Thank you for the high effort post! I was about to start copying game files from my old computer out of frustration.
Thank you, i have already marked the help article as un-helpful 
The link worked, thank you @ SkolliVoxel
You blessed soul. Thank you for doing what Blizzard fails to.
Bump…Thank you for this.
Blizzard seriously needs to fix this for ALL of their old games that customers have bought. I bought this game through the “new” battle net and now couldn’t even play it because of Reforged only download system. Blizzard should have the decency to have all games available for download since customers “own” the code. Having a Wow account for over 15 years almost without relapse and this disappointed me.
Thank you again.
I am late to the party here… I have Mac OSX version WCIII: RoC and the license key on my account. I used to be able to play on Battle.net approaching Reforged being released and Blizzard pushing updates that eventually rendered my laptop unable to keep up with the latest updates. Is there a way to play my version on battle.net with my friends using Reforged? All the installers I find are broken and you stated and my Macbook Air indicates the link you provided was for a Windows file, any chance you know of a workable link for OSX? Thanks in advance for any guidance.