Parliament is expected to pass unprecedented emergency legislation this week. But that, in many ways, is the easy bit. What matters is how ministers exercise the powers that parliament gives them. And what matters even more is how the courts respond to any challenges. Public confidence in the judiciary depends on it.

The Coronavirus Bill itself has 85 clauses and runs to 57 pages. And those are just the broad principles: detailed provisions are to be found in 27 schedules covering another 264 pages. A large-font version of the bill produced for the visually impaired weighs in at an extraordinary 780 sheets of A4.

Nobody can be expected to read and understand the entire bill, although the explanatory notes (73 pages) provide a helpful introduction. There is also a detailed explanation for the Health Secretary’s declaration that his bill is compatible with the human rights convention. Broadly speaking, Matt Hancock argues that the powers he is seeking are proportionate to the risk coronavirus poses to public health.

The bill is vast in scope. It allows for emergency registration of health professionals to meet staff shortages. To ease pressure on coroners, a doctor who has not seen the deceased will be able to certify the cause of death. If there are not enough judicial commissioners to approve the use of investigatory powers by intelligence and law enforcement agencies, temporary commissioners can be appointed quickly and more time will be allowed for the after-the-event approvals. There will be formal powers to close schools as well as ports and airports. Existing restrictions that allowed people in England to be screened for coronavirus and detained if necessary will be extended to the rest of the UK. There are powers to restrict events and close premises — but not parliament. Courts in England, Wales and Northern Ireland will hold virtual hearings, with none of the parties present, in civil, family and non-jury criminal cases; they will livestream hearings to ensure open justice but it will be an offence to make unauthorised recordings or rebroadcast the proceedings. There will be powers to facilitate the transportation, storage and disposal of human remains. Elections will be postponed for a year.

The main challenge in the Commons today will be to the length of time the legislation is to remain in force.

The main challenge in the Commons today will be to the length of time the legislation is to remain in force. In the government’s view, this should be two years — although some decisions taken under the act— such as registration of professionals — will remain in force indefinitely and ministers will have the power to extend all other provisions for six months at a time, any number of times.

A cross-party backbench amendment in the name of Harriet Harman and David Davis would limit the legislation to one year — although the power to extend it would apparently remain. The Labour front bench want the legislation to be renewed at intervals of six months.

Whatever happens to these amendments, MPs are expected to pass the bill today. It will then go to the Lords, which will debate it tomorrow and on Wednesday. The legislation will come into force before the end of this week. Not all provisions will be brought into force immediately; others may be ended early. Different powers may be extended or revoked in different parts of the United Kingdom.

Some changes could not wait. Regulations were made by ministers under current public health legislation in both England and Wales on Saturday afternoon closing entertainment venues immediately and requiring businesses such as restaurants and pubs to stop serving food or drinks for consumption on the premises.

These regulations came into force before they could be considered by parliament. Powers granted under the new legislation may well be exercised at a time when parliament is unable to meet. Should we be alarmed by the breadth of these powers and the speed with which they are being implemented?

There is certainly scope for arguing that specific powers are unnecessary. But, as the blogger David Allen Green said at the weekend, taking emergency powers demonstrates that “those responsible for dealing with an emergency are doing so in accordance with the rule of law”. It is not as if ministers are claiming the power to act in any way they see fit: they cannot exceed the powers they have been granted by parliament, broad though those powers certainly are.

And emergency powers should always be time-limited — though there is scope for arguing what that limit should be. Of course, things will never be quite the same again and some of the changes might be worth keeping — such as live-streaming judicial proceedings. But these changes need to be assessed carefully before decisions are taken on whether they are retained permanently.

Crucially, there is no attempt in the Coronavirus Bill to restrict the availability of judicial review. If ministers or others in authority misuse or exceed the powers they were granted by parliament, the courts will be able to intervene. Knowing that there is a “war” on, I am sure they would think carefully before doing so. But the judges are our last line of defence. As Lord Atkin said in a celebrated dissenting judgment delivered during the dark days of 1941, “in this country, amid the clash of arms, the laws are not silent. They may be changed, but they speak the same language in war as in peace.”