A fundamental fact about government is that it possesses the means of compelling compliance by physical force if necessary. (religion-online.org)
The same majority opinion also refers the tax as too small to actually compel compliance and is therefore just a small optional tax for those who choose to forgo health insurance. (firstthings.com)
Police carry weapons in order to compel compliance from potentially hostile people, and to protect themselves. (politics.stackexchange.com)