[Broken_Hippo]

If folks can steal other people's stuff, it is not a good shelter. It doesn't matter if it is drugs or any other personal belonging. If folks can steal drugs, they can steal money as well.

Build better shelters.

But more than that: You can require certain things, like not being violent with other folks. That they clean up their own messes. Provide mental and physical health care at the shelter and offer medical help in weaning off drugs. This won't work in an environment that isn't safe and secure, for both the person and their stuff.

More unpopularly: Require that they shoot up in the proper location, where there are sharps boxes and so on. Get treatment for folks or employ trained staff to help folks shoot up (if you can't help folks stop, we can do it as safely as possible).