Sure, except (at least in Germany) they get the short end of the stick.
They generally have to enter into non-competes, prohibiting them from working for other agencies or companies. They are only paid when the temp agency actually has work for them. They generally get zero benefits compared to regular employees. They also tend to be paid pennies and don't benefit from labour agreements (because unlike their regular employee co-workers they're not allowed to unionize). Basically, they're like independent contractors, except they're not independent.
Temp agencies in this form weren't even legal in Germany until a few years ago (well, about a decade now).
I doubt that would be the question of law the appeal hinged on, but some of the procedural issues with the case. The government never fully explained how the evidence abroad was legally located or acquired, which could unravel the entire case.
Most of the case was based on evidence found on the laptop seized when Ulrich was arrested. Even if the Server evidence was thrown out (which itself doesn't seem likely, IMHO) Ulrich still would've faced substantially the same case.
The chat-logs that were evidence for all but one of the attempted murders he was indicted for were found on the server, which might be part of the reason he wasn't charged with those. Though those probably would've been difficult to get a conviction on in anycase, since no one knows who the "hitman" really was.
I honestly don't see how contracting out your domestic spying to a foreign country makes it legal in the face of a law restricting such surveillance. For example, if the local police want to search your house, they need to go to court first for a warrant. They can't just hire a 3rd party to break into your house and then try to use that evidence against you. (the 'government agent' doctrine)
Then again, if judges continue to refuse plaintiffs who challenge these practices, then it really doesn't matter what the law is.
You're right from a 'getting a case in court' stand point, but I don't think most of the spying/tracking is about getting a case to court, and as the SilkRoad trial MIGHT have shown, the gov't just needs a way to show that they were able to track you down. They can probably make up a way that they did it after the fact if their initial search was in fact illegal.
Please don't turn this into a debate about SilkRoad, I'm using that as an example of something that might have happened, I'm not saying it did or didn't. That is for other threads.
Well, there's that whole FISA secret court thing. There's basically a body of law that's above the law in the U.S.. As a Canadian, I expect there's something similar here too. These courts ostensibly aren't interested in prosecuting people for the usual crimes like murder, drug dealing, etc.. Just the nasty terrorist-type stuff that will get just about any bill, no matter how abusable, passed by the powers that be. Of course, there's always mission creep.
Even if this is a Democratic-only concern (which I don't think it is), this would be an easy one for a Senator in the minority to sell to the Chairman as a personal favor. It would just be a subpoena to answer some questions; the Chairman wouldn't be signing up to actually do anything like sponsoring legislation.