If an approach chart says "GPS required", do I need GNSS capability to fly it?
If you don't have DME/DME/IRU and are RNAV (non-GNSS) capable, can you legally fly the approach?


The chart the OP refers to is shown below.


As you can see from the STAR (standard terminal arrival), which is not an "approach" you have to have either "GPS" or a "DME/DME/IRU" capable RNAV system. Older RNAV systems that do not have an IRU (inertial reference system) would not qualify for this STAR.