States and localities that refuse to use local resources to enforce certain gun-control measures may have a plausible legal path. But courts are starting to block efforts that move beyond that.

On Tuesday, U.S. District Judge Brian C. Wimes, an Obama appointee, ruled that Missouri’s “Second Amendment Preservation Act” (SAPA) is unconstitutional.

“SAPA’s practical effects are counterintuitive to its stated purpose,” Judge Wimes wrote in his opinion. “While purporting to protect citizens, SAPA exposes citizens to greater harm by interfering with the Federal Government’s ability to enforce lawfully enacted firearms regulations designed by Congress for the purpose of protecting citizens within the limits of the Constitution.”

Like many other Second Amendment sanctuary-style laws, this one sought to prevent state officials from cooperating with federal officials to enforce specific federal gun laws. But Missouri went further. It purported to nullify any national laws and regulations it considered infringements of the right to keep and bear arms within the state’s borders.

“All federal acts, laws, executive orders, administrative orders, rules, and regulations, regardless of whether they were enacted before or after [SAPA] that infringe on the people’s right to keep and bear arms as guaranteed by the Second Amendment… shall be invalid to this state, shall not be recognized by this state, shall be specifically rejected by this state, and shall not be enforced by this state,” the law said.

Some of those nullified laws spelled out by SAPA were more symbolic or forward-looking, such as its rejection of any federal act “ordering the confiscation of firearms.” Others, like the rejection of “any tax, levy, fee, or stamp” imposed on firearms and ammunition, directly run afoul of longstanding federal law.

The Pittman-Robertson Act, for instance, has levied an excise tax on all sporting firearm and ammunition purchases since 1937. The National Firearms Act (NFA) of 1934 requires owners to pay a $200 tax stamp when registering certain weapons, like short-barreled rifles and suppressors. Violations of the NFA could cost a person up to 10 years in federal prison. And, while gun-rights advocates may disagree with the legality of the NFA or be sympathetic to attempts to circumvent its requirements, state nullification is not a path that has ever worked to overturn federal law.

That’s because, as Judge Wimes found, the U.S. Constitution’s Supremacy Clause preempts any state law that conflicts with federal law. The Oregon state court of appeals applied that basic principle in a dispute between state and local law a few weeks back as well.

In mid-February, a three-judge panel for the Oregon Court of Appeals ruled that a Columbia County Second Amendment sanctuary ordinance violated the state’s firearm preemption law. That ordinance, like SAPA, barred all local employees from enforcing any gun law that originated outside the bounds of the county. But it also went the route of attempting to nullify gun laws made outside the county.

“It should be self-evident from the compounding evidence that the right to keep and bear arms is a fundamental individual right that shall not be infringed and all local, state, and federal acts, laws, orders, rules or regulations regarding firearms, firearms accessories, and ammunition are a violation of the Second Amendment,” the ordinance said.

It also created a civil penalty to be enforced by private citizens for violating its decree. And again, like SAPA, it now finds itself invalidated.

Compare the experiences of those two “sanctuary” laws that strayed into nullification with many of the still-standing resolutions and ordinances from around the country. An estimated 1,900 counties have become some form of “Second Amendment sanctuary.” Yet, almost none have run into the same trouble in court. That’s because the vast majority of those other ordinances only involved withholding local resources toward enforcing a disfavored law.

The resolutions that spread across Virginia like wildfire in 2019 are one example. The recent showing of many sheriffs in Illinois this year in response to the newly passed “assault weapon” ban is another. Both efforts experienced backlash from gun-control supporters and elected officials but neither has lost in court. That’s likely because the government officials involved did not attempt to declare the laws passed by higher levels of government invalid within their jurisdictions. Instead, they focused on denying the use of local resources to enforce those laws.

The Supreme Court’s decision in 1997’s Printz v United States provides solid footing for state and local officials to refuse to spend resources enforcing federal laws they believe are unconstitutional. In that case, the Court found the federal government could not compel sheriffs to temporarily conduct background checks on handgun purchases while it set up its own system. Many “sanctuary” policies draw their legal footing from the principles at play in the case, even when a locality is challenging a state law rather than a state challenging a federal law.

But, as the Missouri and Columbia County cases show, it’s one thing to restrict the use of its resources to enforce gun laws it believes are unconstitutional, it’s another to attempt to declare them null and void. That tactic did not work for South Carolina in 1832, and it’s unlikely to work today either.