Quantitative Restrictions

Explicit limits, usually by volume, on the amount of a specified commodity
that may be imported into a country, sometimes also indicating the amounts
that may be imported from each supplying country. Compared to tariffs, the
protection afforded by QR's tends to be more predictable, being less
affected by changes in competitive factors. Quotas have been used at times
to favor preferred sources of supply. The GATT generally prohibits the use
of quantitative restrictions, except in special cases, such as those cited
in Articles XX (which permits exceptions to protect public health, national
gold stocks, goods of archeological or historic interest, and a few other
special categories of goods), or Article XXI (which permits exceptions in
the interest of "national security"), or for safeguard purposes, when the
appropriate procedures in Article XIX have been followed.