AUKUS is under pressure, not from adversaries abroad but from state governments at home. While Canberra drives the security pact forward, Australian states are the ones that that hold the constitutional levers over the land it will need, through their powers of zoning, environmental approvals and handling Indigenous rights.

States are already dealing with legal and political friction relating to this, and concerns over reliability of the United States as an ally may lead states to question the long-term value of their sacrifices.

The real opposition to AUKUS may ultimately come from Adelaide or Perth.

South Australia isn’t just building submarines—it’s building legal tension. The state recently fast-tracked legislation to smooth the path for AUKUS infrastructure at Osborne, but critics aren’t buying it. The Greens and local community groups say the new laws sidestep environmental oversight and shut the public out of decisions that reshape their suburbs. What looks like streamlined defence policy to Canberra looks more like executive overreach to inner-city Adelaide.

Western Australia may be next. With HMAS Stirling flagged for upgrades and nuclear training added to the mix, the state government will soon face its own AUKUS-related planning headaches. WA’s environmental protections are some of the strongest in the country. We may soon find out just how far they’ll bend under the weight of trilateral ambition.

In both states, the issues are the same: land, laws and legitimacy. AUKUS might be stamped with the Commonwealth seal, but the real action is unfolding on state soil. Zoning battles, nuclear questions, and Indigenous land rights aren’t just planning issues; they’re pressure points in our constitution. While no one wants to wade too deep into black-letter law, AUKUS is fast becoming a case study in how fragile Australia’s federal balance really is. While defence might be a national responsibility, it’s built—quite literally—on state foundations.

State concerns go well beyond turf wars. States are being asked to make permanent, often politically difficult changes, such as rezoning coastal areas, approving nuclear-related facilities and navigating complex heritage protections. But in return, they face uncertainty.

When asked about AUKUS, US President Donald Trump responded with his own question— ‘What does that mean?’—sending diplomatic shockwaves through Canberra.

Alliances, once assumed to be stable, can become suddenly transactional. If a future US administration walks back or redefines its AUKUS commitments, states will be the ones left with the consequences. They will have bent their planning rules and stirred local opposition for a security benefit that might vanish based on election results in Washington.

These pressures are converging. As a result, it is Australian states—not just the courts or Canberra insiders—that could prove the most formidable challengers to the next phase of AUKUS.

That opposition won’t necessarily be loud, dramatic or even headline-grabbing. It may look like legal challenges, bureaucratic roadblocks, and slow-walked approvals. It may come as litigation over environmental law and cultural heritage, or as quiet political resistance: premiers may begin to ask whether the federal government has done enough to justify the upheaval.

None of this means AUKUS is collapsing, but it does mean closer attention needs to be paid to states, especially Adelaide and Perth. Canberra cannot afford to treat AUKUS as a closed federal project. The government can’t assume consent, but rather earn it, and not just with federal funding announcements or defence white papers. AUKUS will increasingly require political legitimacy beyond Defence briefings and federal budgets.

To achieve that, the Commonwealth must engage more transparently with state governments, clarify the legal boundaries of implementation, and address public concerns about environmental, cultural, and economic impacts. Otherwise, the most significant resistance to Australia’s biggest strategic undertaking in a generation may come not from foreign adversaries, but from within—one zoning dispute at a time.