In the U$.$S$.$ and a number of other$$ countries, individuals wishing to make organ donations at the end of their life have to$$ "opt$-$in$,"$ i$.$e$,$ affirmatively agree to be a donor. In$$ contrast, a host of other countries have an$$ "opt$-$out" policy, whereby you have to explicitly state that you do not wish to be a donor to reject the organ donation option.