I am a frequent fog bank/ low cloud flyer.
1640ft (500m) is the Spark max.
I have performed about 12 flights under those circumstances and have never had the issue of the craft not coming back down.
Quite the opposite.
I have to slow the craft down because the ultrasonic sensors become confused and
shut off with the warning land immediately....but who listens to that?
Without the ultrasonic sensors, the craft cannot "see" the ground.
My first landing in this condition I hit the ground pretty hard because it will not stop.
Ever since then, I expect the craft not to slow down - so I do so manually.
And enjoy!
As far as breaking laws in the US, under section 336 is not a law but guidelines for safe flight.
However, we are now flying under Part 101E and trying to find out how that reads.