Is there a way to apply a different ASM policy with iRules

Yes, you could use the

ASM::enable 

function. For more details on this see: https://devcentral.f5.com/wiki/iRules.ASM__enable.ashx

Or, even better, you can also use an LTM policy to do this.

Hi,

 

Niels provided the code to change ASM policy within an iRule as you asked.

 

But the question is why don't you change the ASM policy in the LTM Policy which assigned the default ASM Policy?

 

You only have to create a new rule in this policy. This policy can also be used to change pool assignment...

 

iRules are really powerful, but always try with policies before writing irules.