The issue is cloudy for Trump..because it is cloudy for everyone due to the Media spin and misinformation since this issue arose.
Stop and frisk is not illegal. What is illegal..is the wholesale stopping and frisking of random people without any articulable reasons tied to the law;
In New York, the statute is 140.50 of the Criminal Procedure law (still in effect) which allows the stopping, questioning and possibly the frisking of certain individuals if certain criteria are met. Basically, to get to the frisk part, the cop has to articulate a real fear for his safety and spell out what led him/her to that point.
What happened here in NYC is, we had a succession of ambitious, boob Police Commissioners obsessed with Compstat and crime reduction, that basically started tracking stops..ordering more..and unleashed a virtual army of rookies into crime ridden neighborhoods who searched everyone indiscriminately, hence the outcry.
When the media got ahold of it, "Stop and Frisk" was attributed as an NYPD policy, not a CPL provision which it actually is.
Its basically a tool to keep Officers safe, that was abused and morphed into a stat generating machine.
(ironically, it kept crime down as well, because bad guys stopped routinely carrying guns, lol)
Just some perspective