Here's what I have found out from the USFWS (U.S. Fish and Wildlife Service) office.
They directed me to the following PDF which explains much of the 1973 Endangered Species Act (ESA).
On the first page on the right side you will see the definition of "Take"
I think it clearly implies you can not hold them or even attempt to hold them.
http://www.fws.gov/endangered/esa-li...ESA_basics.pdf