where can I locate private security use of force limatation case law and policy

You should be able to access either Westlaw or LexisNexis---two computerized legal research programs at the Clark County Law Library located in downtown Las Vegas.

They have reference librarians there who may be able to assist you with your search.

You can also use, for free, the facilities at the William Boyd School of Law located on the UNLV campus.

Finally, you can type your keywords--security guards, detention, etc. into an Internet Search engine and you may get some applicable hits.