I agree that's how the law should be interpreted, however as mentioned in the article above posted by Missy, it is still a bit of a grey area. Your work computer is work property. And especially working as an accountant or any position that requires public trust and confidentiality, the employer will do what they can to protect themselves from any lawsuits, privacy issues, and infiltration (hacking). Based on my understanding, if they have to defend themselves in court, they can basically say that plugging your device into a work computer constitutes permission to access your data in order to protect themselves.
Here is the bit from the article mentioning the grey area:
It’s precisely those mixed-used situations that BYOD policies, and the technology that supports them, are meant to address. The most common way companies do that is by installing mobile device management (MDM) software on employees’ devices. And according to a 2014 white paper by the IBM-owned company Fiberlink (which sells an MDM product called MaaS360), any MDM solution worth its salt “should be able to parse what information it can access and what it cannot.”
Still, the situations that might impel your company to scroll through your photos or peek at your emails—let alone punish you for them—are pretty rare. Hill mentions two: when your employer “is subject to a lawsuit in which you could be a witness, or if you and [your] employer get into a dispute.”
But the law is only beginning to grapple with these questions, and in the meantime, usage agreements for company devices, Rosenberg says, usually aren’t written broadly enough to govern conduct on personal gadgets, too. That’s all the more reason, in her view, why BYOD policies are so important: “Otherwise you’re arguing about what an employer can and can’t do. If you have a policy that defines it, everybody knows what’s up.”
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