It's legal to pour liquor into another vessel (e.g. a Bloody-Mary glass); add things to it (whereupon "infusion" takes place, albeit for minutes rather than days); and then serve it.
Would it be legal to pour the alcohol into another vessel (e.g. a jar); add stuff to it; allow infusion for a period of time; pour the resulting mixture into a cocktail glass; and then serve it?
Could it be that simple? If not, why not?
Or better, just put whatever you want infused into the original bottle. If you need room use a little alcohol in a regular drink, then you have plenty of space for the infusion material.
There might be some food-handling issues, especially if they’re putting bacon/pork in the mix.
Yes, it is that simple.
The only violation is refilling a liquor bottle. That is a federal offense.
https://www.ttb.gov/public_info/5170-2a.htm
My understanding is that - in Houston- every bottle has an id, and tax is paid after the bottle is emptied, not before. I suspect there is a similar issue here.