I've already argued against your first quote in the post. The privacy acts only apply when the government is getting the data from third parties such as from an email provider or ISP. In this case the image is directly communicating back to their servers and no third parties are involved. Communications between two parties are not subject to the privacy laws when you are one of those two parties.
The target is irrelevant in the case of legality. The only additional protections a journalist has is on not revealing their sources. This doesn't impact or interact with other emails so no sources could be compromised via a tracking pixel. Being "shady" isn't illegal and I wouldn't even say a tracking pixel is shady. The closest approximation of what this tracking pixel is doing is as a read receipt for a piece of mail.
If you want to quote "United States v Jones in 2012" against others you should probably be aware of what the presiding judges actually ruled. It was determined that the action was illegal only because physically attaching the device was considered trespass of private property not because the tracking of the vehicle's location required a search warrant.
If you wanted to make a similar argument you would have to instead refer to the Computer Fraud and Abuse Act to cover something similar to digital trespass. A tracking pixel does not violate that law under any circumstance that I'm aware of.
Any action by the government that can be seen to be chilling toward a free press can be interpreted as a violation of the first amendment. It's not as black and white as you make it out to be, and remember new precedents are being set all the time. They're also in the ninth circuit which is historically hugely favorable to these kinds of cases. You get a strong enough case, a lot of money and a creative lawyer, you might be able to make some caselaw here. There's at least a baseline argument for it.
That said, target is not irrelevant for illegality. There's also an issue of ethics in targeting other lawyers; if I was the defense lawyer this is the issue I'd be pushing like crazy with the judge, ethics panels, etc. Right or wrong, they can do something with that, esp. if they can get some discovery that proves there was actually an attempt to target -- that would be huge. (And they're not allowed to delete any documents to that effect since they are the government).
The target is irrelevant in the case of legality. The only additional protections a journalist has is on not revealing their sources. This doesn't impact or interact with other emails so no sources could be compromised via a tracking pixel. Being "shady" isn't illegal and I wouldn't even say a tracking pixel is shady. The closest approximation of what this tracking pixel is doing is as a read receipt for a piece of mail.
If you want to quote "United States v Jones in 2012" against others you should probably be aware of what the presiding judges actually ruled. It was determined that the action was illegal only because physically attaching the device was considered trespass of private property not because the tracking of the vehicle's location required a search warrant.
If you wanted to make a similar argument you would have to instead refer to the Computer Fraud and Abuse Act to cover something similar to digital trespass. A tracking pixel does not violate that law under any circumstance that I'm aware of.