1) It seems like a perfectly reasonable request—provided you have a clear understanding of what “foreign” means in this context.
2) What’s the story here? What’s the history? What were people flushing (no, I don’t *really* want to know) that inspired officials to print and post this sign? (My constant theme: every sign, like every government regulation, has a history.)
Thanks to Charles for contributing this image (which is from an office building of Canada’s federal government).