Can a non-copyable member be used as alternative to make an object non-copyable?

A class with non-copyable member is said to be also non-copyable. From SO, to make a class non-copyable these are the options:

1. Use boost::noncopyable

2. Declare constructor and assignment operator as private.

   class foo 
   {
       private:
         std::mutex _dummy;
   };
   
   

Question: Will inclusion of a dummy non-copyable member be used for similar purpose and for simplicity? What are the down-sides?