Anyone know the specific reference from the UPC or the IRC which would address stub-outs at a sink? Is there a specific reference for PEX?
Also if you have a good illustration it would be useful too. Thanks in advance. 
Tubing and fittings shall be installed without placing stress on the connection. Stress on connections frequently occurs when tubing is not properly strapped at changes of directions. This from one brand of PEX.
For Wirsbo / Uponor brand see about page 23
https://www.uponorpro.com/~/media/Extranet/Files/manuals/plumbing/AQUAPEX%20Install_HB_10-05.aspx?sc_lang=en
Thanks Barry and Stephen for the help. I’ve got some good illustrations now.
I wanted something concrete to use because this is a homeowner install and the guy is overly confident in his work. He also failed to install a trap below the basement shower which I discovered by depressurizing the house using the bath and range exhausts. It smelled wonderful. I still can’t find a reference outside of the manu. specs. you guys directed me to, but they will probably be enough. I’m sure the owner will still argue his “floating valves” are good enough. 