I'm a little confused by what you're asking because you haven't stated what exactly came in the mail. My guess is what came in the mail was one of two things either A) a civil demand letter for money from Target or B) a subpoena to appear in court. If it was a subpoena or any kind of court document DO NOT ignore it. If it tells you to be in court on a certain day or time, make sure you appear. If on the other hand it was a civil demand letter for money then that is less serious, but they have a right legally to send it to you. Hope this answer helped a little.
Melissa Levine is a licensed attorney in Massachusetts. All answers are based on Massachusetts law and should not be construed as legal advice. No attorney-client relationship is formed by Attorney Levine answering your question. It is advisable to consult with an attorney about your personal legal concerns.
I am unclear on what you are considering ignoring. If you think you will get a summons in the mail, do not ignore it otherwise a warrant will be issued for your arrest. In many jurisdictions the retailer can charge you a fee for security expenses and there may be a statute that allows them to do so. I have seen attorneys tell client to not pay it. However, the store can file a civil suit and even request the police to file charges. I suggest complying with what the law dictates.
Marijuana is against federal law. Federal law supersedes state law. A person could be charged and convicted for marijuana related crimes such as possession, cultivation, distribution, manufacturing, transportation, and conspiracy.
Although you don't explain it the question, "should we ignore the mail . . ." indicates to me you are receiving what are know as civil demand letters. They will continue for a time and normally reflect greater and greater amounts to satisfy them. I consistently advise clients to ignore these letters. This is an extremely common issue on this site. If you look at them (Btw I am not recommending that you do so) you will see various recommendations out there. My impression, however, is that a distinct majority of responding attorneys advise as I do to ignore them. If you receive something from the courts, do not ignore that and retain counsel immediately. I think the chances of that happening at this point if it has not already happened is slim and none. Do not post any further details on the Internet.
If the letters you are getting ask you to pay a civil fine, ignore them. This is one of those times in life where if you ignore something it actually will go away. Rarely, if ever due to the collection agencies pursue the matter in small claims court.