Can you show me where it is illegal for a private citizen to contact Russia? Can you show me evidence that Trump contacted Russia illegally?
To save you some time Googling, the answer to both of those questions is no.
Yes, but you're having to work extraordinarily hard to miss a couple of pretty basic points.
First, if
@Victoria33's "incidental information" scenario is correct, then the Russians in question were already under surveillance. The "incidental information" would have arisen if and when these Russians were in contact with Trump's team, no matter who called whom.
Law enforcement involvement for such incidental information only comes into play if the contacts between Russians and Trump's team included some sort of illegal activity. They could have talked about the weather, in which case no problem; or they could have talked about a bribe -- in which case, as I noted above, the FBI is obligated by law to pass on the information to the relevant law enforcement agencies.