Here's one such guideline:
"No part of the flag should ever be used as a costume or athletic uniform."
The flag "should not be embroidered on such articles as cushions or handkerchiefs and the like, printed or otherwise impressed on paper".
Hmmmm. I wonder how carefully the Republicans adhere to that one?
Why, look! Here's a whole website of stuff for sale called (appropriately) "Republican Market."
Republican Market: Flag Fanny Pack
Republican Market: Stars and Stripes Shoulder Bag
Republican Market: Flag Tote Bag
Republican Market: Elephant with Flag Polo Shirt
Republican Market: Crossed Flags Silk Tie
Why, imagine that.