これはjust cause, good causeのことでしょうが、下のビデオのunder the banner of 'national security'（安全保障の御旗のもとに） 49:03 も同じ意味で使えます。
https://www.youtube.com/watch?v=hkORJR8cb5g 0:59 画像 they hope to galvanize low-wage workers under the banner of civil rights, and position economics alongside racial justice.
https://www.youtube.com/watch?v=hkORJR8cb5g 0:33 the character was born under the MGM banner.
