Typically these laws are needed to explain why some otherwise possible process does not occur. For example, the decay of a proton to produce a positron and a photon has not been seen.
Conservation laws are a set of rules that forbid all such non-occurring decays .
If the rules are simple, they can be extremely powerful and govern a huge variety of processes. The risk in setting these laws is that there may be some very rare processes that we have not yet observed that may not respect the laws we state them today. If such decays are found, we will have to downgrade at least one of these laws to an approximate conservation law . So Far Observed As far as we know, there are nine exact conservation laws that govern all particle decays. All of these conservation laws are consequences of the Standard Model of particle interactions .