Tex. Bus. & Com. Code § 661.005
(a) If a subject or medium of payment of a contract, security, or instrument is the European currency unit or a currency that has been substituted or replaced by the euro, the euro is a commercially reasonable substitute and substantial equivalent that may be:
(b) A person may perform any obligation described by Subsection (a) in euros or in the currency or currencies originally designated in the contract, security, or instrument if that currency or those currencies remain legal tender, but the person may not perform the obligation in any other currency, regardless of whether that other currency:
(c) The following occurrences are not considered a discharge of, do not excuse performance under, and do not give a party the right to unilaterally alter or terminate a contract, security, or instrument:
Added by Acts 2007, 80th Leg., R.S., Ch. 885 (H.B. 2278), Sec. 2.01, eff. April 1, 2009.