Is it legal to buy and sell frequent flyer miles?

• yes
  It's easy and legal to purchase and sell frequent flyer miles directly to and from an airline.Can I buy and sell airline miles?
• no
  It's easy and legal to purchase and sell frequent flyer miles directly to and from an airline.Can I buy and sell airline miles?
• it depends on the time of the year
  It's easy and legal to purchase and sell frequent flyer miles directly to and from an airline.Can I buy and sell airline miles?