On the one hand, all is fair in love and war and free agency. On the other hand, the NFL does seem to operate on something of a mafia code of ethics or code of conduct, and playing games with trade comp and money matters like this certainly seems like a violation.
Also consider, the "free agent legal tampering" period is a big time media blitz for the league. These sort of shenanigans by the Ravens threaten it - the whole point is to announce deals and get viewer eyeballs and fan engagement. If deals can't be announced because agents and players are afraid of other teams backing out then there is no point to the window at all. I don't know what the league will do, if anything, but would not shock me at all to see them punish the Ravens with the loss of a pick or something.