Should there be a law

NO! There should not be a law!
My thoughts even tho they may not matter to anyone. The owner of any automobile is just that, The owner. He or she can do what ever makes them happy.
I find that any car is just part of a mechanical build. When I see a brand that has been changed to use something other then what can from a factory I check out how the persons engineering and mechanical skills were put to use. Its interesting how it was done and if you look at it with an open mind you would even pick up some pointers for something you may do somewhere down the road.
Now dont get me wrong, My Dodge will be all Dodge, Although I almost went with a 7004R trans but decided to stay with a 904 instead. My Corvette is all Chevrolet. Yep Chevrolet shares a spot right beside my Dodge. When I look at them I see a body formed around lots of parts that have been made outside of a Dodge and Chevrolet plant.
So again, no there should not be a law. Open your mind to something different! Enjoy the hobby!
Rod