The charge is very specific. The evidence is published where anyone can see it. By international law (1969) and by American law (1989), it is unlawful to perform laboratory modifications to a virus that make it more infectious or more deadly. These are called "gain of function" modifications.
"Whoever knowingly develops, produces, stockpiles, transfers, acquires, retains, or possesses any biological agent, toxin, or delivery system for use as a weapon, or knowingly assists a foreign state or any organization to do so, shall be fined under this title or imprisoned for life or any term of years, or both."A SARS-like cluster of circulating bat coronaviruses shows potential for human emergence.
This article published in the journal Nature Medicine in 2015, describes experiments in which a Coronavirus that infects Chinese bats is modified to enable it to bind to the human ACE-2 receptor. The work was performed at UNC Chapel Hill and at Wuhan Institute of Virology in China. In the 'Acknowledgements' section, Fauci's NIAID is listed as primary funder.
The charge does not depend on the facts that the current COVID epidemic derives from a Chinese bat virus that is said to have "mutated" so as to bind to the human ACE-2 receptor.
I invite readers with a legal background to comment on whether Dr Fauci could be charged and tried based on this evidence.