I think this is one of those things that doesn't require a written policy mostly because it would be hard to enforce. I have never seen a sign in any store banning customers from reading magazines without paying for them first. However, unlike a library, stores can't just let customers 'borrow' a magazine if they are not going to purchase it, even though I certainly am guilty of reading them while waiting on line at the supermarket. In fact, I think magazines are placed at the checkout so people will look at them while waiting and decide to buy one.

I'm actually surprised the employee said anything to you. It sounds like you intended to buy the magazine, and I don't think there's anything wrong with looking at it first and even reading an article. I don't think he was calling you a thief, but maybe they have a problem at that particular location with too many people hanging out reading the magazines, and he's keeping an eye on everyone.

This is an interesting issue, and I'm curious to hear how Target responds.