In Norway, employer even have only limited rights to access things like your employer owned devices if they are personal to you, on the basis that it would be an invasion of privacy unless a lot of steps have been taken to prevent you from accessing or storing personal information on it.

Though in a case like this where they have evidence that implies wrongdoing, that would be sufficient to search equipment the employer owns or have financed. The barrier for searching private equipment is massively higher, though, and would normally require going to court.

Personally I'd never consider working for anyone that demanded a clause like what you outlined. I understand their liability concerns, but the at the same time if they won't trust me, then I can't trust them.