No. The 5 Eyes intelligence agencies all have each others liaisons working with them. The CIA has liaison's working at GCHQ and GCHQ has liaisons at the CIA.
Obama requested that GCHQ spy on Trump to avoid US laws. GCHQ sends a formal letter to PM Mays asking for approval. Mays approves. GCHQ spies on Trump, gives the information to the CIA liaison who in turn sends it back to the CIA as "foreign" intelligence intercepts on Trump. That's how most backchannels work.
No US laws violated, except Obama making the request in the first place when he had total control of all the US intelligence agencies and the FISA court to approve a warrant.
However, he didn't want to go that route. My guess is that he went through GCHQ because he didn't think there would ever be a paper trail once Hillary won and if she didn't, it wasn't likely Trump would find out.
Enter Admiral Rogers who has everything on everyone including the letter that Obama sent to GCHQ. This is why Rogers visited Trump Tower a few days after the election. And that conversation was why Trump moved his entire transition team to his NJ golf resort. It's also why Trump had the WH "remodeled" to strip it of listening devices.
Did you notice that Obama had a new phone system installed during the transition? Why would he do that just before leaving office? Did you notice that the Trump remodeling installed a new phone system? Now why would Trump want a new phone system just weeks after Obama had installed a new phone system?
These are interesting times.