

There were no founding fathers who wrote a document to include this “ultimate check”.
“We The People”. The first three words establish the philosophical model of the constitution. “We The People” willed it into existence.
The 6th Amendment guarantees the right to a trial by a jury of the accused’s peers. Not the judicial branch of the government. Not the government in general. It guarantees the right of the accused to take the case directly to a quorum of 12 members of “We The People”.
The founding fathers did write a document that included this ultimate check.
A judge would merely be a steward conducting proceedings and a jury would just mete out justice based on the vibe of the matters before them.
They do. Generally, the “vibe” is that legislated law is just and proper, and the jury should apply it as written. Generally, jury nullification is not a factor.
But we are contemplating the special case. Here, we are not constrained to the general case. Here, we are considerong the conditions under which the law itself is determined to be unjust, such as the “Fugitive Slave Laws” we actually had on our books. Here, we can consider a corrupt legislature enacting unjust laws.
Are we forced to jail an abolitionist for aiding and abetting a former slave in escaping his “owner”? Are We The People truly compelled to abide by the evil acts of a reprehensible legislature?
We are not.
The fact that justice won’t always be done is not in any way a justification for rendering the unjust verdict demanded by a corrupt legislature.
It is absolutely a mixed bag. Ideally, jury nullification would never be used, because none of our laws would be unjust or improper to apply.
But, we have had “Fugitive Slave Acts” on our books for the majority of our history: acts that criminalize providing aid and assistance to escaped slaves, or failing to deliver them to their “owners”.
We cannot pretend our legislature has never been corrupt, or will never be corrupt in the future. Jury Nullification is an important check on an out-of-control legislature.