Inspired by Free Radical's post, I think I have figured out a simpler and clearer way to say what I want to say about Walras' Law.
Ask yourself the following question:
Q. Assume an economy where there are (say) 7 markets. Suppose 6 of those markets are in equilibrium (with quantity demanded equal to quantity supplied). Is it necessarily true that the 7th market must also be in equilibrium (with quantity demanded equal to quantity supplied)?
This is an open book exam, and you may Google if you wish.
This is a question for both macroeconomists and microeconomists. (And for non-economists too.)