There's not really a law that says officers can't "stop and identify", in Washington there is NO law that says they CAN.
There are court decisions that cover actions like this that say officers have to have Reasonable Articulable Suspicion to detain a person.
Some of those decisions that shed some light on this are:
Probably the closest to what you asked for is here:
Which covers what the Stop and Identify Statutes are, which states have them, and some more detail as to what is required.
Have fun reading.