No legal grounds, it is very much the equivalent of quitting within the first 90 days (I think, I'll look it up if it matters).

There is the ethical consideration, but that is the one of the hard truths of life; employment is not secure until you've already been working for 90 days. And then, only slightly more so.

So, in short: it would be bad sense for them to stop searching for a candidate, as a back up should I cancel and as potential future hires. And they would be naive to think I've stopped my job hunt, not all lines of inquiry resolve at the same rate. It is easy for them to predict that I may receive competing offers.

p.s.: I'm not a defaulting moloch leech, I swear. The early acceptance was to allow me to give very early notice in my current position and to facilitate a smooth exit that leaves everyone happy.