Earlier quoted context omitted.
And if you have any record of use, even a medical marijuana card, you are prohibited from purchasing a firearm.
Are you sure this is true? I was under the impression you can buy firearms legally without background checks at all in much of the USA
Edit: form 4473 question 11e asks if you are an unlawful user of drugs such as marijuana and reminds you that it is still federally illegal. You will fill out this form if you purchase a gun from a licensed dealer. Lying on this form is itself a felony.