En documentos legales generalmente se define en una cláusula especial. Para mejor entendimiento del concepto doy la siguiente referencia:

"SECTION 10.16 Judgment Currency

(a) Each Seller's obligations hereunder to make
payments in Dollars (the "Obligation Currency") shall
not be discharged or satisfied by any tender or
recovery pursuant to any judgment expressed in or
converted into any currency other than the Obligation
Currency, except to the extent that such tender or
recovery results in the effective receipt by the Buyer
of the full amount of the Obligation Currency expressed
to be payable to it under this Agreement. If for the
purpose of obtaining or enforcing judgment against a
Seller in any court or in any jurisdiction, it becomes
necessary to convert into or from any currency other
than the Obligation Currency (such other currency being
hereinafter referred to as the "Judgment Currency") an
amount due in the Obligation Currency, the conversion
shall be made, at the rate of exchange determined, in
each case, as of the day immediately preceding the
Business Day on which the judgment is given (such
Business Day being hereinafter referred to as the
"Judgment Currency Conversion Date").
http://www.secinfo.com/d11a8p.22y.d.htm