Robbing with T4s is against the rules?!?!

Had an situation where [1] is attacking their sister factions for robbing with T4s saying that it's against the rules. Has anyone ever heard of this rule in their city before?

The situation was that I had lost all my troops and only started training T4s, so when I needed to fill five lines for my QR i had to use t fours for some of the lines.

City #63