Rulebook page 26
Infantry, artillery, mechanized infantry, tanks, and AAA (antiaircraft artillery) can attack and defend only in territories. Only
infantry, artillery, mechanized infantry, and tanks can capture hostile territories or convert friendly neutrals. All can be carried
by transports.
Just makes it consistent with the already existing rules. AAA cant be used to take ownership of a territory. Existing rule considered everything but the issue of guardianship of dutch territories. This ruling just adds to that rule and makes it include everything instead of everything but the dutch territories.