How can I fight being separated for failing BLC after refusing to go because of migraines, and then being forced to attend anyways?

If you can't go to something that is required because of medical reasons, the commander can either bar you from reenlisting or request a med board. You have to be able to do what is required.

Going to turn it around a bit - You said constant migraines, so obviously you have gone to your primary care a number of times, were referred to specialists to determine the cause (don't know if they found an underlying cause for you) and if there was nothing to do, you were referred to a MEB.

At least, that's how it is supposed to work. Did you ever see your docs about it before BLC? Did you go to sick call while you were at BLC? If none of this is documented aside from a trip or two to the docs, then you did yourself a large disservice.

Having said that, are there routes you can take now? Yes. First, did you explain all this to your commander? At your counseling for the BAR, you should have been informed of your right to dispute or appeal the bar. I assume you have less than 10 years of service, so the rebuttal/appeal would go up to the first O6 to review. However, all of this without any medical evidence just sounds like you making a convenient excuse.

What you can do now? Two things - contact legal assistance and explain your situation. They can better advise you regarding steps about rebutting/appealing the bar (an appeal is done at the time of the BAR counseling normally). Second is that you need to go see your primary care and get the ball rolling about why you're having headaches. However, if there is nothing to show an underlying condition that is causing your headaches, it will just come across as that convenient excuse again.

Now, if you HAVE been going to the doc and have documented treatment, etc. you are in a much better position regarding the BAR. If you have been seeing the docs and they still can't figure out what's causing your migraines, then you should have been put on a profile limiting your activities and if they exhausted the 'limit of military medical care' and you still had constant migraines, you should have ended up in the IDES system for medical retention evaluation (and possible medical separation).

Bottom line: If you haven't already, talk to your commander regarding your migraines, and if you have, call legal assistance to see what your options at this point are.

As SFC Kelly Fuerhoff pointed out the commander MUST chapter or bar you. Even if they only barred you and then removed it later, it takes approval from your first General Officer Commander to return to an NCOES after failing or missing a class date. It also requires endorsement from the same first GO to cancel or defer a date for NCOES. You can't simply refuse to attend NCOES.

If constant migraines are hindering you from completing schools then you are not medically fit to be retained in the Army. You need to go see a provider and have the very real discussion about medical separation. Once your med board is initiated you can't be separated for the NCOES failure unti the med board completes.

You will be separated. Whether it will be an administrative separation, which would be disadvantageous to you, or a medical separation, that would advantageous to you, is all that's left to decide. The only way to stop your separation would be if your Commander wanted to fight for you and was willing to push for your endorsement by the CG. Some CGs and Division CSMs absolutely refuse to sign off on rescheduled NCOES except for extreme circumstances. No NCOES means no promotion. No promotion means you can't stay in the Army.