Like many things that can act as poisons, small amounts are not harmful. The thing that sets mercury (and other heavy metals apart) from many other materials is that our bodies take a long time to purge it.
Therefore it is necessary to be cautious with even relatively small exposures to mercury and other heavy metals if contact occurs regularly.
Playing with mercury a few times isn't likely to be harmful. Handling it regularly (such as through a ritual that is performed often) very well could be harmful.
The government really cannot effectively regulate such things other than to require proper warnings and recommending medical testing that could show that mercury is building up in someone's system.
I think of it the same way I think of the risk from lead from shooting firearms.
The government can't regulate it well. Even their current actions place a huge burden on people, most of whom face no real risks.
However, if you often work at or shoot at an indoor range with poor ventilation, you should have your doctor run tests to make sure you aren't building up unsafe levels of lead in your system.
I know a number of people who ended up with elevated lead levels due to being very active in indoor shooting matches in the winter time. These are people that shoot and are around people shooting a lot and didn't have trouble with elevated lead levels until they reached a point where the exposure was increasing the amount of lead in their systems faster than their bodies purged it. Then it became a problem.
People need to be aware that the risk is there and take appropriate precautions, however the government really cannot properly regulate the exposure because there are too many factors involved and what is safe for one person might not be safe for another.
It's something that the people who choose to involve themselves in the activities need to be aware of and take responsibility for on their own.
Here's some folks selling a "liquid metal alloy" which is most likely the same stuff:
Liquid Metal Alloy
"A non-toxic liquid metal to use instead of mercury. This alloy is liquid down to -20° C (-4° F). It can coat objects to make them conductive. It can coat glass to make mirrors. It can make low friction electrical connections."
Disclaimer: I have no connection with the linked site, whatsoever.