The small legal switch that turns an Act on

SI 2026/1157 was made on 3 November 2026 and turns on parts of two planning laws in England. Its main lesson is not brownfield land or housing targets by themselves, but the quieter word that makes a law start to bite: commencement.

Here is the short version. Parliament has already passed the Planning and Infrastructure Act 2025 and the English Devolution and Community Empowerment Act 2026. But passing an Act does not always mean every part of it works straight away. Often, Parliament gives a minister the power to choose when parts of the Act come into force. That ministerial switch is called commencement.

This matters because a law can exist in public without yet doing its main job. You can read it. Lawyers can cite it. Ministers can point to it. But until the relevant section is commenced, the legal duty may still be waiting at the door.

SI 2026/1157 is one of those switches. The instrument says that, from 26 November 2026, section 58 and Schedule 2 of the Planning and Infrastructure Act 2025 come into force, so far as they have not already been commenced. Section 58 inserts a new Part 1A into the Planning and Compulsory Purchase Act 2004, and that new Part 1A requires strategic planning authorities to prepare a spatial development strategy.

A spatial development strategy is a high-level plan for an area. It is not the same as a single council deciding whether one estate gets planning permission. It is more like a map of priorities: where housing should broadly go, what infrastructure matters across council borders, and which policies are of strategic importance to the area. The 2025 Act says such a strategy may deal with the amount and distribution of housing, affordable housing and strategic infrastructure, but it must not specify particular sites where development should take place.

So who decides? First, Parliament created the framework by passing the parent Acts. Then the Secretary of State for Housing, Communities and Local Government used commencement powers to decide when selected provisions would start. Matthew Pennycook, Minister of State, signed SI 2026/1157 by authority of the Secretary of State on 3 November 2026. After that, strategic planning authorities must do the work of preparing the strategies.

The phrase strategic planning authority is doing a lot of work here. The Planning and Infrastructure Act 2025 defines it to include a strategic planning board, a combined authority, a combined county authority, certain upper-tier county councils, and certain unitary authorities in England. In plain terms, this is planning above the level of many individual district councils. It is meant to deal with questions that do not stop neatly at a council boundary, such as transport links, housing numbers or infrastructure.

The instrument also turns on, from 4 November 2026, section 39 of the English Devolution and Community Empowerment Act 2026, so far as it was not already commenced. Section 39 amends section 12G of the Planning and Compulsory Purchase Act 2004. It requires the Secretary of State to make regulations prescribing the desirability of prioritising development on land that has been previously developed as a matter strategic planning authorities must have regard to when preparing a draft spatial development strategy.

That sentence is a good example of how law hides power in small words. To have regard to something means an authority must take it into account. It does not automatically mean that factor wins. If a council must have regard to flood risk, for example, it cannot ignore flood risk. But the final decision may still weigh flood risk against housing need, transport, cost and national policy.

So the brownfield part is not yet a full brownfield-first rule. Brownfield land usually means land that has been previously developed, such as an old factory site, a disused depot or empty commercial land. The commenced section requires ministers to make further regulations about the desirability of prioritising that kind of land. The missing link is that the public still cannot see those brownfield regulations in this instrument.

That matters because the future regulations will decide the practical force of the promise. They could say what counts as previously developed land. They could say what evidence an authority must collect. They could set exceptions for land that is contaminated, at flood risk, badly connected, too expensive to clean up, or not actually deliverable. Or they could do much less, requiring authorities only to record that they considered the issue.

This is the difference between a slogan and a rule. Brownfield priority sounds firm. The legal text switched on by SI 2026/1157 is more cautious. It says ministers must prescribe the desirability of prioritising previously developed land as something to be considered. It does not ban greenfield development. It does not tell an authority what to do where brownfield land is too costly to remediate. It does not publish the test an examiner will use if a strategy says there is not enough usable brownfield land.

There is another missing piece. The instrument does not name the authorities first caught by the 26 November 2026 duty. It does not say which places are ready, how many staff they have, what evidence base they will need, or how the cost of preparing and examining these strategies will be met. The explanatory note says a full impact assessment has not been produced for this instrument because no, or no significant, impact on the private, voluntary or public sector is foreseen. It points instead to impact assessments prepared for the two parent Acts.

That is a thin official account for a switch that activates a new strategic planning duty. The parent Acts may have assessed the wider policy. But a commencement decision also has real-world timing effects. If an authority must begin preparing a strategy before the brownfield rules, procedure regulations, guidance and funding position are all visible, it has to plan around uncertainty. That uncertainty is not theoretical. It can mean extra consultancy work, duplicated evidence, slower local plans, and arguments later about whether the strategy was prepared under the right assumptions.

Who benefits? The Secretary of State gains a clearer statutory framework for steering strategic planning. Strategic planning authorities gain a formal role, though it comes with duties attached. Developers and infrastructure promoters may benefit if cross-boundary plans make land and transport decisions clearer. Owners of usable previously developed land may benefit if brownfield desirability strengthens the case for their land.

Who pays? Local planning authorities, combined authorities and strategic authorities may pay through staff time, evidence gathering, consultation and examination costs unless central funding covers them. Council-tax payers may pay if authorities meet those costs from existing budgets. Communities may pay in a different way, if big choices about growth and infrastructure move into a strategic document that many people have not yet learnt how to follow.

That is why commencement is worth noticing. It is a small legal word with a large democratic effect. It lets ministers decide when Parliament’s words become public duties. In this case, the switch has been flicked for the strategy machine, but the public still has not been shown the brownfield operating instructions.

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