Once they sign and faxed it in, no.
LOI is basically a 3 year contract with the fourth being a player option. Easiest way to explain it.
Now the only thing correct with this is the spelling, so I responded:
LOI is a 1 year only contract. Player can go elsewhere if he wants right away, but he can't play for a year, and I'm pretty sure he can't be on scholarship either.
As a real life example, Lavelle Hawkins signed with LSU in the 2004 class. I'm not sure he even made it to fall camp as he decided it wasn't right for him, enrolled in a JC and played, and then signed and played for Cal in 2005. So a player can sign and flip, but he can only do so at a significant cost to himself.
If this wasn't what the original poster was getting at, I'm too dense and you'll have to explain it to me.