Your command will make the decision as to the type of punishment that will be appropriate (i.e. Article 15, or court martial). Of course you have the option to refuse an Art 15, but that would likely force the command to request a court martial. Either way you are entitled to consult a military defense attorney for free, I would contact them and if you can consult with an attorney who understands reserve/guard issues as well. If you were not on active duty, generally the UCMJ will not apply to drug use (even if you were positive at drill). But, if you were on active duty at and before the time of the test, UCMJ applies. It is kind of a confusing issue with the reserves / guard. Even if you were not on active duty, you can still be adsep'ed for drug use in the reserves or guard. In any event you should not make a decision to accept a general discharge without first consulting with an attorney.
From the desk of T. Edmund Spinks, Esq. P.L.
304 Plant Ave. S. Suite 100
Tampa, FL 33606
Disclaimer: legal information is not the same as legal advice -- the application of law to an individual's specific circumstances. Although we go to great lengths to make sure our information is accurate and useful, we recommend you consult a lawyer if you want professional assurance that this information, and your interpretation of it, is appropriate to your particular situation. This information is not intended as legal advice for an individual situation, it is only provided as information.
I agree with Mr. Spinks, but would also like to add that the National Guard's response is typically a bit different than the active component. While all those options are available, a courts martial is very unlikely. Additionally, depending on your state, you may not have an absolute right to demand courts martial in lieu of an article 15 as you would an active duty Article 15.
Assuming you are on title 32 status (regular drilling National Guardsman), you are governed by state law (typically a state military code), rather than the UCMJ. If you were on title 10 status, than the UCMJ applies fully.
Army regulations still apply and a drug positive requires that a separation action be initiated. This will probably go to a separation board, where you will have a chance to prove that separation isn't warranted. You should be given the opportunity to have detailed military counsel (or at least consult with a military attorney) if this occurs. You may also hire your own attorney. If you are served a separation board notification you may not have a lot of time to look around for an attorney.
This answer does not, nor is it intended to, create an attorney-client relationship, but is offered solely for informational purposes. Since the facts of each case are different, it is important to seek out qualified counsel with whom information can be shared and assessed under an attorney-client privilege so that competent and tailored advice can be provided.
You will lose your GI Bill, all educational assistance (See, e.g. 38 United States Code 3011) and all civil service retirement credit. The good news: a general discharge is a "honorable discharge". However, as a E-7 I would request a board!