Hobby breadboard wiring guidelines to stay within legal RF/EMI limits?
There isn't a reason to worry about exceeding limits with a breadboard, the FCC allows for building of single devices with no testing:


  What does this mean for a hobbyist? Very little, actually, depending
  on what you’re doing. The FCC allows a hobbyist to build up to five
  devices of a single design for personal use with no testing
  whatsoever. If you are contacted by the FCC (or anyone else) about a
  matter of spectrum interference, immediately stop using the device,
  don't use it again, and you should be okay. Stick to the ISM bands
  (13.56MHz, 27.12MHz, 40.68MHz, 915MHz, 2.45GHz, and 5.8GHz, +/- a bit
  for each) for added comfort.
  Source: https://www.sparkfun.com/tutorials/398


The point at which you may get in trouble if you are unintentionally radiating large amounts of RF on bands that are in use by people that care. For example: A electronic billboard was leaking RF on a cellular band, the phone company saw the leak with their equipment and complained to the billboard company. If the company didn't fix the leak they then could complain to the FCC, and they could take action with fines, ect. 

It's unlikely that you'll build an unintentional radiator with a breadboard that would get someones attention. You might however build an intentional radiator (like an FM radio) that could disrupt a radio a few 10's of meters away. If you're building an intentional radiator that's a different story.