police power

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The inherent authority of a government to impose restrictions on private rights for the sake of public welfare, order, and security.

from the GNU version of the Collaborative International Dictionary of English.

• (Law) The inherent power of a government to regulate its police affairs.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun law The inherent power, incident to sovereignty, of a state to regulate and exercise reasonable control over matters of public health, public morals, public safety, and in general, all things relating to the general welfare.