Hi @rcarlson39 - I cannot think of a way to prevent this within groups. In fact, with few exceptions (such as an instructor-created Discussion topic as a graded, group topic) anything in a group is pretty much fair game for students to delete--especially items that they themselves created. One example I often mention in my own training workshops is even if a faculty member disables the ability for students to create their own Discussion topic in the course Discussions area, the same does NOT apply with groups. They can always create their own Discussion topics in a student group.
About the only recommendation I can think of is that you would have to create the Collaboration yourself and invite the students one-by-one to each specific Collaboration, retaining your ownership rights and doling out editing privileges accordingly.
Interestingly, this very topic is due to be updated with this weekend's new release, as outlined here: https://community.canvaslms.com/docs/DOC-8835-canvas-production-release-notes-2017-02-18#jive_conten... . As of this weekend, instructors and TAs will be listed to be included in a Collaboration. That still may not address, however, cases where a student created the document and, therefore, would have the ability to delete it, as well.
Hello @rcarlson39 ...
I wanted to check in with you because there hasn't been any new activity in this particular discussion topic since @kblack 's response on February 17th. Have you had a chance to review Ken's response at all? If so, did that help to answer your question? If it did, please go ahead and mark his question as "Correct". However, if you are still seeking assistance with your initial question, please let us know that, too. For now, I'm going to mark your question as "Assumed Answered", but that won't prevent you or others from posting additional replies below. I hope that is okay with you. Looking forward to hearing from you soon, Ruth!