Can my son claim himself if he qualifies as a dependent on my return?

My son qualifies as a dependent on my return.  He is 21, was a full time student for 5 months, lived with me for more than half the year and I paid for all of his support.  He worked part time, made $11,248.  He wants to claim himself on his return.  I know we can't both claim him but is he allowed to claim himself if he could be claimed on mine?  I do want to claim him and I want to be able to tell he's not allowed to claim himself.