From Justice Kennedy's opinion:

Exposing governmental inefficiency and misconduct is a matter of considerable significance, and various measures have been adopted to protect employees and provide checks on supervisors who would order unlawful or otherwise inappropriate actions. These include federal and state whistle-blower protection laws and labor codes and, for government attorneys, rules of conduct and constitutional obligations apart from the First Amendment. However, the Court’s precedents do not support the existence of a constitutional cause of action behind every statement a public employee makes in the course of doing his or her job.

So I don't think it would be "minting" any right at all - it would, in fact, state plainly a right that even the majority found to exist.  In fact, every one of the dissenting opinions also mention such a right, though they related it to the First Amendment.

From a legal standpoint, it wouldn't matter if a court later ruled that the warrant was good.  What mattered is that Ceballos acted in good faith.  At the time he acted, he believed it would be a criminal act to withold vital evidence.

The defense attorney might not have been the proper place to go - perhaps the judge might have been a more neutral arbiter.  But the action was justified with what he knew at the time.

XT