More inclusive/formal synonym for "grandfathered in"?

Solution 1:

Just so it's abundantly clear where this unforgivable expression actually comes from:

The term "grandfather clause" originated in the American South, way back in the 1890s. At that time, several Southern states developed and enforced the clause as a way to get around the 15th Amendment, and thus prevent black Americans from utilizing their then-newfound right to vote. The "grandfather clause" stated that black men could only vote if their parents or grandparents were able to vote before the year 1867 — which was, conveniently for racist lawmakers, many years before black Americans were permitted access to voting rights.

So yes. "Legacied" is a good alternative.

Solution 2:

Here are a couple of words that could work when describing a grandfather clause (which always makes me think of Santa).

"Legacy" (n.)

something that happened in the past or that comes from someone in the past

Merriam Webster

Legacy is a common alternative to "grandfathered." For example: "There are three bars in town that are permitted to stay open until 4am, because of their liquor license legacy." I should note, that in common usage it is often coined "legacied" which I cannot find a definition for, but would be used as in, "The liquor license has been legacied." Meaning that the license was covered under a grandfather clause.

"Heritage" (n.)

a : something transmitted by or acquired from a predecessor : legacy, inheritance

b : tradition

Merriam Webster

This speaks more to the "we've always done it this way" mentality than a legal permission.