under the banner of

under the banner (of) (something)

1. Identifying oneself with a particular title, slogan, etc. Before they officially formed their nonprofit as you know it today, they went under the banner "Green Jobs for Good."
2. With the stated support for or of something. This usage is always followed by "of (something)." We're holding the rally under the banner of equality and tolerance. All are welcome.
See also: banner
Farlex Dictionary of Idioms.

under the banner of

1 claiming to support a particular cause or set of ideas. 2 as part of a particular group or organization.
See also: banner, of
Farlex Partner Idioms Dictionary
See also:
  • banner
  • wash (one's) hands of (someone or something)
  • wash hands of
  • wash one's hands of
  • wash your hands of
  • wash your hands of somebody/something
  • wash your hands of something/someone
  • for (one's) (own) sake
  • for sake
  • keep in sight
References in classic literature
Archers from the New Forest and the Forest of Bere, billmen from the pleasant country which is watered by the Stour, the Avon, and the Itchen, young cavaliers from the ancient Hampshire houses, all were pushing for Christchurch to take service under the banner of the five scarlet roses.
The White Company
Though the defectors led by Mustafa Kamal under the banner of Pak Sarzameen Party (PSP) and others doubt the divide between London and Karachi the MQM Pakistan Chief Dr Farooq Sattar two weeks ago announced to completely take out Altaf Hussain of the party constitution, defying the pressure from London few hours earlier in form of reaction to removing Altaf Hussain name and photo of the party flag.
Banners urging death for traitors of country put up in Karachi