private property rights? not quite. otherwise malls/stores would kick out the people asking for donations.
Don't people soliciting donations have to have permission?
I know that when we did "Girl Scout Cookies" when my girl was little, we had to have permision from the store owner (Wal-Mart, grocery, etc.) to set up a table out front.
At stores or malls where groups are seeking donations, it's most likely if not certain they've the approval of the property owner or manager.