Yes AlmostAtheist I believe your argument is extremely valid. I like it, and I'll probably use it.
When people say 'physical laws' they meen things that we can always count on as a result of certain events. Since they are so dependable and always uccur, people call them 'laws'. (Not a preticularly good word for them I know.)
Wikipedia: A physical law, scientific law, or a law of nature is a scientific generalization based on empirical observations of physical behavior. They are typically conclusions based on repeated scientific experiments over many years, and which have become accepted universally within the scientific community.
It's the same way with the 'law' you mentioned 'law of supply and demand' It's not a real law it's just called one by some people because it's so certain that it works every time. Nobody invented it, it's just a fact.
Law of Demand: As prices fall for a particular good or service, the demand for that item will increase. Vice-versa. (No government or individual had to say 'If a price falls you must buy more stuff or go to jail.')
Law of Supply: As the price of a particular good or service increases, the supply for that item will also be increased. Vice-versa. (Same thing, nobody had to specificaly say 'It's now the law, when something is expensive, buy less.')
These 'laws' just occur on their own when certian conditions are met. (IE. people sell stuff.)
Same with the physical 'laws' when a lot of mass get together, they have more gravity.
So when people say "All laws require a Law-Giver." they are wrong and right...
REAL laws require a law giver: Law is the set of rules or norms of conduct which forbid, permit or mandate specified actions and relationships among people and organizations.
But things that happen just because certain conditions are met are not real laws, call them what you will, they are just truths theories or facts.
Unless of course said creationist believes that the planets and ateriods are sentient beings that will be punished if they disobey the law... If someone says that to you, just stop arguing and walk away... carefully... 'cause your not gonna get anywhere.