If you have reasonable suspicion the work doesn't comply with regulations, then I'd say deciding not to do anything also isn't without risk.
Because, if at a later date, something like a fire happens, that puts people at risk, then especially if there is any evidence that you chose to ignore things, then I assume you could become liable in some way.
Aside from the legal stuff, building regs are mostly there for a good reason, so it's not really good form to let something that you know might be dangerous to persist. Not all of the building regs are about safety critical things but a lot of them are, not limited to fire stuff.