The Court was asked to review cases. Those cases relate to a doctrine known as qualified immunity.
...a doctrine which shields police from lawsuits...
Qualified immunity shields government officials (police, in this case) from civil lawsuits (suing for damages - officials can still be held criminally accountable).
...conduct that does not involve a “clearly established” violation of the law...
The QI only applies when there is not a "clearly established" violation of the law.
That last phrase is the real killer. Courts require the aggrieved party to cite previous cases with EXACTLY the same set of facts. Of course, no two cases are exactly the same, so the courts have effectively given police officers blanket immunity to civil claims...
"... cases that asked the court to revisit the existing doctrine. This doctrine protected police from lawsuits concerning police conduct, where their conduct didn't involve an obvious crime."
“... cases that asked the court to revisit a doctrine which shields police from lawsuits for conduct that does not involve a “clearly established” violation of the law.”