The Legality of Retail Arbitrage and Dropshipping

[Johnny Cash]

Hello,

I'm looking to try out retail arbitrage and dropshipping, but I'm unclear on the legality of it all. I've done Google research, and it's still all confusing to me.

Let's say I wanted to do this . . .

1. Find an item at Walmart.com which is selling for more on eBay.
2. List that item on eBay for the current (eBay) selling price.
3. Wait for someone to purchase my item, then I purchase the same item at Walmart's reduced price, and have it shipped to the eBay buyer directly from Walmart.

Would this be legal, yes or no?

If not: What are the limits (i.e., how far could I go with it before pissing someone off), and what could the (realistic) consequences be?

I know there are some arbitrage and dropshipping experts here (I'm looking at you, Quasar), so I hope my questions can be settled once and for all.