Add a new rule “The Laws of time” to the ruleset:

The subrules to this rule are considered the Laws of Time, which are a number of rules designed to prevent Cronocrime running rampant. Travellers do not necessarily have to follow the provisions stipulated in the Laws of Time, but if they break such a sitpulation, they may be guilty of commiting a Cronocrime.

And add a new subrule to it entitled “No vandalizing other people’s Time Machines.”:

Travellers may not change another Traveller’s formula without permission of either that Traveller or the Arbiter.

These rules were intentionally left vague to give room for future proposals on this subject.