my understanding is that there used to be a pretty prevalent scam in which a firm would send something of value unsolicited and then bill the recipient. When the recipient did not pay, the firm would harrasss the recipient and do whatever nasty thing they could to get the money. If you were someone that sold stuff like that from Fingerhut, i.e. marking up just 10000%, one could get a pretty penny if even 10% of the recipients were extorted to pay.
To combat this, in the US there are laws, as cited below, that pretty much give huge right to the recipient of unsolicited merchandise. There are two exceptions. Merchandise that is sent for inspection is to be returned. For instance I used to get calls from firms that would offer to send me stuff for free and if I liked it they would then bill the company. The assumption was that the purchasing department in a moderately sized organization would pay for stuff management wanted without too much checking or hassle. The law still provides a level of protection as the merchandise can be returned and the time frame is not set in stone.
My feeling is that, at least in the US, the recipient should be protected. Look at it this way. I order a box of pens from office depot. Instead of pens, the send me a printer. It could be that someone in my office steals it. Am I then liable for the printer?