The are some clubs that go "racing" under colregs rather than the RRS. I think these are often called Beer can races.
What is the situation if one of these beer can races is going around a racing mark (laid by the national authority for the purpose of racing by affiliated clubs) at the same time as a boat really racing under the RRS? Can a boat racing under RRS assume that another is also under RRS because they are rounding a racing mark, flying a club pennant and for all practical purposes acting like a racing boat?
What if we actually know that the other club is a beer can racer, and has neither accepted the rules, nor has a safety audit nor insurance to cover racing? I assume we need to treat them with colregs and thus take early and substantial action if we are give way, and hold our speed and course if we are right of way etc.
But how does that work when the beer can racer contests a mark rounding? Colregs simply doesn't cover mark roundings as it only provides for avoiding collision and has no provisions to allow a boat to sail her course around an imaginary point that is marked by a buoy that is not a substantial obstruction ? Moreover what if the beer can racer actually acts like they are under the RRS by trying to establishing inside overlap etc.
Ideally boats under different rules can just stay well clear of each other, but you can't do that if they are rounding your marks! So any advice on interpreting the rules would be appreciated.