§ 20-147 - 155 of the Virginia Code pertain to marital agreements.

Married persons may enter into agreements with each other for the purpose of settling the rights and obligations of either or both of them, to the same extent, with the same effect, and subject to the same conditions for agreements between prospective spouses, except that such marital agreements shall become effective immediately upon their execution. If the terms of such agreement are (i) contained in a court order endorsed by counsel or the parties or (ii) recorded and transcribed by a court reporter and affirmed by the parties on the record personally, the agreement is not required to be in writing and is considered to be executed. A reconciliation of the parties after the signing of a separation or property settlement agreement shall abrogate the marital agreement unless otherwise expressly set forth in the agreement.

The agreement may contract the parties with respect to:

1. The rights and obligations of each of the parties in any of the property of either or both of them whenever and wherever acquired or located;
2.  The right to buy, sell, use, transfer, exchange, abandon, lease, consume, expend, assign, create a security interest in, mortgage, encumber, dispose of, or otherwise manage and control property;
3.  The disposition of property upon separation, marital dissolution, death, or the occurrence or nonoccurrence of any other event;
4. Spousal support;
5. The making of a will, trust, or other arrangement to carry out the provisions of the agreement;
6. The ownership rights in and disposition of the death benefit from a life insurance policy;
7. The choice of law governing the construction of the agreement; and
8. Any other matter, including their personal rights and obligations, not in violation of public policy or a statute imposing a criminal penalty.

As stated above a reconciliation of the parties after signing a separation or settlement agreement voids the premarital agreement.  If you try to void the agreement under contract law, the statute of limitations (limitation of action in Virginia) is polled (ceases to run) during the marriage.  After the agreement is signed then the only way a premarital agreement is not enforceable if the person against whom enforcement is sought proves that:

1. That person did not execute the agreement voluntarily; or
2. The agreement was unconscionable when it was executed and, before execution of the agreement, that person (i) was not provided a fair and reasonable disclosure of the property or financial obligations of the other party; and (ii) did not voluntarily and expressly waive, in writing, any right to disclosure of the property or financial obligations of the other party beyond the disclosure provided.

Any issue of unconscionability of a premarital agreement shall be decided by the court as a matter of law. Recitations in the agreement shall create a prima facie presumption that they are factually correct.

If a marriage is determined to be void, an agreement that would otherwise have been a premarital agreement shall be enforceable only to the extent necessary to avoid an inequitable result.