Why would there be ever one? Being a (former) head of state doesn't include being above law, and it shouldn't ever be that way.
Politics
@politics on kbin.social is a magazine to share and discuss current events news, opinion/analysis, videos, or other informative content related to politicians, politics, or policy-making at all levels of governance (federal, state, local), both domestic and international. Members of all political perspectives are welcome here, though we run a tight ship. Community guidelines and submission rules were co-created between the Mod Team and early members of @politics. Please read all community guidelines and submission rules carefully before engaging our magazine.
well. So, like, there is a norm of not writing them speeding tickets. But there's a few reasons for this. the first being that the Secret Service provides drivers and they're trained to not stop. ever. (they also don't speed, but details.) there's a certain amount of leeway with petty things, and a large part of that is the secret service usually intervenes and intimidates the people/mechants/whatever making the claims so they go away.
Generally speaking, though, the reason these charges are unprecedented is because no ex president has ever committed these crimes. said another way, they're unprecedented because trump's criminality is unprecedented.
As the article mentions, there is no norm, but there is precedent for pardoning former presidents, due to Ford’s pardon of Nixon for Watergate. Trump may still be pardoned if the Republicans win the election.
Rachel Maddow had an interesting piece about how the DOJ kept Agnew from running, with a plea agreement.