Laws are not the same as contractual terms. When I buy something at the store, the only terms I'm agreeing to are the exchange of ownership (implied by tradition as part of the act of sale) and whatever terms are explicitly laid out at the point of sale (return policy, etc.). When I buy a CD, I'm trading my money for the store's plastic disc, but I'm not agreeing to any restrictions on what I do with that disc once I get it home.
That's just because we're not a Libertarian society. But in a Libertarian society, that's exactly how IP would work. It would be in the form of contracts, either explicit or implied.
In a Libertarian society, assuming courts are operated by the government, the government will have to set default contractual terms because otherwise it could not enforce contracts. Whatever those defaults are, people are always free to change them. Likely, if the default included no IP or IP that most sellers didn't find satisfactory, restrictions on what you could do with the CD once you got home would be included in the sale contract.
Those restrictions are part of the law, not the sales contract. If I violate them, it won't be the seller (the store) who comes after me, it'll be a third party (the copyright holder, or law enforcement) who had no part in the sale and is not acting on behalf of the seller; and I won't have violated any agreement, I will only have violated the wishes of third parties I've never met and politicians who don't represent my interests.
Right, because we don't have Libertarian IP in this country. If we did, you would likely have to enter into a contract with the rights holder to buy a CD. This could easily be made efficient and streamlined and there would be a large incentive to do so. As I said, you'd probably have to show some kind of ID card that indicated you had entered into a contract with the distributor of the movie in order to enter a movie theater. It wouldn't be hard to make this efficient.
Note that the terms could be much worse than the ones in the United States. With IP terms set by law, the terms are a balance between creators and consumers and include things like fair use. With IP terms set by contract, the terms are much more in the control of the creators and likely would include much more restricted fair use rights. This is why Microsoft uses EULAs.