Jonno D'Addario says:
Over the past few days, Banksy street pieces have been appearing around New Orleans. This one is in my neighborhood, and the timing seems to coincide with the third anniversary of you-know-what this week.
Someone else took a photo of this one in the Uptown neighborhood of New Orleans. It references a local (in)famous anti-graffiti crusader named Fred Radtke, aka "The Grey Ghost", whose one man mission to eradicate street art and tagging in NO involves painting ugly grey squares over everything. (Lots more on him via Google)