The legalities of possessing and selling sinew from wild game animals varies from state to state. I grew up in Indiana and spent my first 5 years learning to make bows there, including several sinew-backed bows that I ended up selling. I left the state in 2007, and as far as I know at that time it was not illegal to possess or sell sinew harvested from white tail deer. Laws can change of course. If you want to know for certain, your best bet would be to call your local warden and ask. If Indiana is the same today as it was when I grew up there, the DNR is so strapped for resources that it is unlikely the warden would try to track you down to check to see if you are using or selling sinew. They have bigger issues to deal with.