"Oh why hello, thanks for calling, no, sorry, I do not own a TV, computer or tablet - I often spend time at my friends home and uses his computer and TV."

This is how people avoid it in Sweden. However, the stores are obliged to report in when you purchase a TV, but all of these things can be avoided by simple lies ("I gave the TV to my friend for his birthday"), and many do so.

Since they are not the government, they cannot legally gain entrance to your property (actually, neither can the government without a warrant, but they cannot get a warrant either). They send you a letter, asking you to sign up to pay the media licence or sign a declaration that you own no such devices.

The declaration - however - is legally binding and there are huge fines for breaking such a declaration. However, they must be able to prove that you do actually have such devices, by entering your property. In most cases, they don't really bother, though.