Different countries define different levels of BAC to be acceptable. Some coutries, eg Sweden allow only zero BAC for the legal driving of a motor vehicle.
In the United States, most states define inebriation[?] by law at a specific BAC (often about 0.10 %). The federal government is forcing a change to 0.08%. In some states, underage drunken drivers are considered legally impaired at lower levels (perhaps 0.02%).
In Australia, the limit is 0.05% in most states and territories, and either 0.02% or zero for inexperienced drivers (learner drivers or those on probationary licenses). It is enforced by random breath testing[?].
See also: Alcoholic units