The conscription issue is that all Iranian males over 18 years of age have to show up for conscription. The military service is slightly more than one year long. The Revolutionary Guards have the first pick when it comes to selection of individuals who show up for the draft. Those people do not have a real choice if the Revolutionary Guards recruitment officer wants them to serve there. But there are also many who actively try to serve their military service in the draft with the Revolutionary Guards because they have better benefits and higher pay.
On May 13th, 2014. See this statement in context.