Can my client even reasonably make the claim in court to his right to bear arms?

My client is telling me that if he goes into court other laws (particularly the 5250 lifetime ban law) will be used to supersede his 2nd amendment right and his "claim" to even bear arms because it is in direct conflict with a lesser law.

Help me understand the Const if I'm misunderstanding how that 4 page contractual document works. From what I understand the Constitution is basically a contract between individuals and the government correct?

My client feels that he no longer has the ability to get treated as a citizen or to claim his 2nd amendment right because there are other laws that expressly deny him that right and can be used to put him in jail if he has a firearm and uses it for the intent purpose of securing his capital land assets etc