How would Texas handle existing U.S. treaties?

In an orderly, well-precedented way, the same way every new nation has. International law has developed specific rules for what happens to treaties when a state becomes independent, and the practical result for Texas is continuity where it counts, with the freedom to choose elsewhere.

There is an established body of law for exactly this

This is not uncharted territory. The question of what happens to a predecessor state's treaties when a new state emerges is the subject of its own international convention, the Vienna Convention on Succession of States in Respect of Treaties, opened in 1978. Dozens of nations have navigated this transition, from the breakup of the Soviet Union to the splits in central Europe, and the law and the practice are well developed. Texas would step into a process the world has run many times.

Boundary and territorial treaties carry over automatically

The most important category is the most stable. Under the 1978 convention, a succession of states "does not as such affect a boundary established by a treaty," nor the rights and obligations relating to a boundary regime, and the same holds for other territorial arrangements. The International Court of Justice has treated this as a rule of customary international law. In plain terms, the treaties that fix borders and govern shared territorial resources do not evaporate when sovereignty changes. They pass to the successor state. For Texas, that means the framework governing the Rio Grande and the Texas-Mexico boundary continues, with Texas stepping in as a party in its own right.

For most other treaties, the tools are continuity and choice

Outside the boundary category, a new state has practical, well-used options. It can succeed to a treaty, declaring that it continues to be bound. It can newly accede to a treaty in its own name. Or, for agreements that do not serve its interests, it can decline. The common pattern is a transition period in which existing arrangements continue while the new state reviews them and decides what to keep. Nothing requires the machinery to stop while that review happens. Continuity is the default, and disruption is the exception a new state chooses, not the rule it suffers.

Many treaties simply convert from internal to international

A great deal of what binds Texas to the rest of the country today are not foreign treaties at all but domestic federal arrangements. Those do not vanish; they change category. Agreements that were internal to the union become agreements between two countries, negotiated in the separation. The substance of who owes what and who gets what does not have to change just because the legal label does. That is the same logic that governs Texas's shared rivers, which convert from interstate compacts into international treaties without changing the underlying division of water.

Texas gains its own seat where it had none

Here is the upside opponents skip. Today, when the United States negotiates a treaty that affects Texas, Texas has no seat at the table; federal negotiators in Washington speak for the whole union, and Texas's specific interests are one consideration among fifty states. As a party in its own right, Texas would represent its own interests directly for the first time, in the agreements that matter most to Texans. That is not a loss of standing. It is a gain.

The bottom line

Treaty succession is settled, well-precedented work. Boundary and territorial treaties carry over automatically as a matter of customary international law, other treaties continue through a transition while Texas chooses what to keep, and domestic federal arrangements convert into international ones in the negotiation. Through all of it, Texas trades a back-seat in Washington's treaties for a direct voice in its own.