Personally, I have used Bitstamp for several years and never had any problem
I traded 4 years, with them, and what? They just deleted my account, and for more than 3 weeks I have not seen all my money
Bitstamp claimed to be licensed in Luxemburg
Their license is received for the "Bitstamp Europe" company, and the Bitstamp company from London itself serves the stock exchange. Ie it's all an illusion.
Below is the CSSF regulator response, from Luxemburg
https://s17.postimg.org/p72m6ikvj/cssf.png