Not at all. To advertise inside each other's premises, you have to enter somebody else's private property, and with some exceptions, right to refuse entry or f

Not at all. To advertise inside each other's premises, you have to enter somebody else's private property, and with some exceptions, right to refuse entry or forbid certain activities on your property is not just allowed, it is what private property actually means. However, I am not the private property of my employer, so unlike this store analogy you need nobody's consent to advertise your job to me. You just call me. This isn't Saudi Arabia where you have to consult my mahram before you offer me a job. Now under the legal theory we have discussed so far, you may imagine that two companies could voluntarily draw up a contract not to hire me just cause that's what they want to do. However, in the United States we don't allow certain types of contracts, even if all the parties to the contract consent. For example we don't allow murder-for-hire contracts, even though both parties have consented to the contract. Similarly, this type of contract is one that is prohibited by law even though both of the parties may agree to it. Specifically the Sherman Antitrust Act prohibits "any contract... in restraint of trade or commerce among the several States". That language is kind of vague but the case law for the last 120 years is clear that this sort of contract is the kind that is prohibited by the act.