Even with the successful attacks (eg. Moscow Subway), additional powers proposed would not have helped. Still we see this call. It is an irrational, but understandable, response when something horrible happens.
At home, I read about teachers calling for stronger search and seizure powers in connection with a teacher getting stabbed by a student in class.
The problem with this argument is that the ability to search the kids bag would not have saved the teacher from his stabbing. There is no indication that anyone thought the kid a risk for this sort of behaviour: just the opposite. So why would anybody think to search him? Do they want to search all students?
Just like the terrorist countermeasures, a shocking event is short-circuiting sound judgement. The logic is that "something should be done". "More teacher powers" is something, therefore we should do it.
While this event does not justify greater search powers, perhaps teachers need them anyway? What's the problem?
Typically, a school will prefer to detain a student and call the police. The police conduct the search. If the school asks the kid to submit to a search, there is a risk that the kid will say "No." Then they will need to insist.
The kid's parents may make a complaint against the school, or the kid refuses to consent to the search, does the school have a legal basis to make the search at all? Are they exceeding their authority by insisting?
This whole topic has been addressed by Rishworth (2004)"Search and Seizure in Public Schools" chapter 7 in Recent Developments in School Law (NZLS 2004 p93). I recently had an update on this in that Law paper I was doing last month, so I figured I'd share what I found out.
Fact is that the search issue has not been challenged in court - yet. It is that "yet" which has schools erring on the side of caution. I will argue that it is this uncertainty that is damaging. Schools need to be assured by explicit statement in law about the likely outcomes should this practise be challenged. The existing authority of the school is otherwise sufficient in practise.
When a teacher searches a student, they risk their actions being examined in court. A school search could be brought to court (a) in criminal cases where the defence moves to exclude evidence found in the search, (b) where student who has been searched claims unlawful trespass, or (c) as a tort of invasion of privacy. Any such case could help establish the legal basis of the search.
One of the reasons why the basis in law is important is because it affects practises that are legal under the Bill of Rights act 1990. Statute trumps Rights. So if a school search is OK in law, then being a violation of human rights is, pretty much, a side-issue.
So, if, as a teacher I demand a student submit to a search, and they say no ... do I get to insist? Do I have any power to search?
The NZ Education act 1989 imposes, on schools, a statutory duty to offer a high standard of education in a safe environment.
With duty comes power - which rests in law on sections 72 and 75 of the act, coupled with s76, which makes principles responsible for the day-to-day operation of the school. One of these powers must be the power to search, or these sections are meaningless.
So - if I, as a teacher, have reason to suspect a student of carrying a weapon, I have a statutory obligation to seize that weapon in the interests of providing a safe environment. The kid may not intend to use it, but it's mere presence on school grounds is a danger - of accident, unintentional use, or misuse by someone else. It is on these grounds that I have confiscated loose sports equipment in a science lab and required that school bags be placed under tables.
In Canada, there is a similar situation where a duty of safe education is imposed but no explicit power to search granted. The Canadian Supreme Court has supported this view (eg. in R vs MRM  3 SCR 393). It seems likely that a similar view would prevail in NZ.
The US situation is similar, though the details vary from state to state. As in NZ, the Federal Bill of Rights acts to protect students from unreasonable search and seizure.
So we see that NZ schools actually have the power they seek. The question under examination is more, "Is it enough?"
The power to search is limited to reasonable searches by section 21 of the NZ Bill of Rights. This is the same limitation placed on the police. What counts as "reasonable" is well established, for example: a police officer needs reasonable grounds, a teacher would just need reasonable suspicion. So teachers, in practise, have greater powers of search than the police. How can anyone argue that this is not sufficient?
So we see that schools have quite broad powers of reasonable search and seizure already. In general, they feel reluctant to use them. Primarily, this is due to misunderstandings about how the NZ Bill of Rights works, and the lack of case law which may make implicit powers explicitly supported. Schools feel underfunded and the cost of defending any of the three possibilities I started with would hurt them.
Students are reported to have become more confident in their rights - often overconfident - with authority-challenging statements like "You can't do that, I know my rights!" reportedly commonplace. It would appear that there is a clear need to educate teachers, students, and parents in the operation of the bill of rights and how this applies to schools. It would also be useful to ensure the smooth and safe operation of schools if teachers could be assured of their implicit powers as an explicit statement in law as well as through familiarity.
What we should not do is allow a rare, shocking, event like the recent stabbing, lead us to hasty legislation which will likely do more harm than good.