Here is the relevant part of the text:
WTO + safeguards
These timetables shall provide for all measures referred to in
paragraph 1 to be phased out or brought into conformity with this
Agreement within a period not exceeding four years after the date of
entry into force of the WTO Agreement, subject to not more than one
specific measure per importing Member 5, the duration of which shall
not extend beyond 31 December 1999. Any such exception must be
mutually agreed between the Members directly concerned and notified to
the Committee on Safeguards for its review and acceptance within 90
days of the entry into force of the WTO Agreement. The Annex to this
Agreement indicates a measure which has been agreed as falling under
And these safeguards are explained here (safeguard measure) for those of us like me who didn't understand the context:
Safeguard measures A WTO member may take a “safeguard” action (i.e.,
restrict imports of a product temporarily) to protect a specific
domestic industry from an increase in imports of any product which is
causing, or which is threatening to cause, serious injury to the
Safeguard measures were always available under the GATT (Article XIX).
However, they were infrequently used, and some governments preferred
to protect their industries through “grey area” measures (“voluntary”
export restraint arrangements on products such as cars, steel and
The WTO Safeguards Agreement broke new ground in prohibiting “grey
area” measures and setting time limits (“sunset clause”) on all
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So, the idea is that WTO members have to either phase out or bring into conformity their protective mechanisms within four years. However, each WTO member may seek approval for one exception to this. If approved, they could continue to use a protective measure for one industry up until 31 Dec 1999.
For example, a WTO member (country) might have a protected steel industry. And they could seek approval for keeping whatever measure they used to protect themselves from steel imports in place until 31 Dec 1999. But they could not keep two measures in place. For example, one to protect their car industry and another their steel industry.
Conclusion: subject to one specify measure really means: unless they have received approval to keep one specific industry-protecting measure in place until that later date. So, yes, it is an exception to the rule for keeping in place a single protective measure until Dec 1999.