Íluvatar's opponents?

[The Saucepan Man]

When Eru’s creations were bestowed with free will, they now had the responsibility to obey Eru (i.e. do good). If they did not have free will, Eru would have simply made them obey. But, since Eru has given them free will, he expects them to obey, anyway. I think it’s an equal trade-off. They have freedom but also responsibility. So, they are expected to be loyal to Eru, but are given the choice of whether to follow through with that expectation or not.

But that isn't really free will. If Eru says to his creations: "OK, you can have free will, but if you exercise it wrongly, then I'm going to stop you" then in reality, they do not have an unfettered free will.

aragronreborn, your analogy to a parent is a good one. Parents exercise a degree of control over their children while they are minors. Those children do not have an unfettered free will because they are constrained in what they can and can't do. But, when those children reach adulthood, they are free to make their own choices and, in doing so, are no doubt influenced by the way that they were brought up. While their parents may seek to guide them, they no longer have any direct control over their children's lives.

So, in the act of creation, Eru was like a parent, imbuing his creations, which at that time had no free will, with certain values. When creation was complete, he gave his creations free will. He could no longer directly influence them. It was up to them whether they adhered to the values he had instilled in them or rebelled against those values. He could only guide them ,as a parent of an adult, for example through the Istari.