What happens to pipelines that cross state lines?

They keep operating, because the oil and gas they carry is something both sides want to keep flowing, and pipelines cross international borders all over the world every day. A pipeline does not stop pumping because there is a border on the map.

Cross-border pipelines are ordinary, not exotic

The premise that a pipeline must shut down the moment it crosses an international line is simply false. Pipelines move oil and gas across borders worldwide, between Canada and the United States, across Europe, throughout the Gulf region. The line on the map is handled by agreement, not by a valve. An independent Texas would treat the pipelines that cross its borders the way every neighboring pair of nations treats theirs: as shared infrastructure governed by a treaty, kept running because both sides profit from the flow.

Most of the Texas network is already Texas-regulated

Texas has one of the most extensive pipeline networks on Earth, and the pipelines that run inside Texas are already regulated by Texas. Pipelines that operate within a single state, the intrastate lines, fall under state authority, and in Texas that means the Railroad Commission of Texas. The vast Texas pipeline grid is therefore largely under Texan control today. Independence does not disturb that. It leaves the in-state network exactly where it is, governed by the Texas agency that already governs it.

The interstate piece converts from a federal matter to a treaty matter

Pipelines that cross state lines are currently overseen at the federal level by the Federal Energy Regulatory Commission under the Natural Gas Act. On independence, a line that used to cross from Texas into another U.S. state becomes a line that crosses an international border, and it shifts from federal regulation to a bilateral agreement between Texas and the United States, the same way cross-border pipelines are governed between any two countries. The substance of who ships what to whom does not have to change. Only the legal category does.

Both sides have every reason to keep the oil and gas moving

This is where Texas's leverage shows. The United States needs the energy that flows through these pipelines, and Texas profits from selling it. Shutting a pipeline would hurt the buyer as much as the seller, which is exactly why it does not happen in real separations. Continuity is the outcome that serves both nations, and a free-trade and energy arrangement between Texas and the United States, which is in Washington's interest too, keeps the molecules moving across the line on stable terms.

The transition is built for continuity

After a vote, the relationship between Texas and the United States is settled through a transition period in which existing arrangements continue while the details are worked out. Pipelines run straight through that transition. There is no day when the gas stops because both governments have every incentive to keep it flowing and the legal tools to do so are already standard practice between neighboring nations.

The bottom line

Pipelines crossing the Texas border keep operating. The in-state network stays under Texas regulation, the cross-border lines convert from a federal matter to an ordinary international agreement, and both nations have every reason to keep the energy flowing.