Edit "rules" to prohibit ownership of a GPS?
Why regular caches only? It is also fun to do a multi without a GPS. I get to calculate the next spot, then plot it on my map with a dried up pen in a rainstorm. Half the time the coordinates are off the edge of my map and I have to go home to print out a new one and come back... Some puzzle caches are very interesting without a GPS as well, but in all honesty many caches are easier with a map than with a GPS. With the best aerial photos out now an experienced map/photo reader can often identify some of the individual trees in a woods.