Yesterday's Federal Court decision striking down the World Youth Day ''annoying laws'' was not a great victory for freedom of speech and the right to demonstrate. Nor, for that matter, for those opposed to public support for a Catholic event. It was, however, a triumph against subjective laws and arbitrary government.

I would not mind betting, however, that lawmakers and administrators read it only in the context of rights to protest, and ignore its wider message, which applies as much to immigration laws, taxation, health, education and social service rules and any amount of modern regulation-making.

The NSW Government's regulations prohibited conduct at declared youth day sites which ''causes annoyance or inconvenience to participants''. A 50-penalty-unit fine (currently $5500) was set for anyone who disobeyed a police officer ordering them to stop.

The Federal Court has struck out the ''annoying'' section, as not specifically authorised by the NSW Parliament. It has left the ''inconvenience'' section intact.

The problem about annoyance is that it is an entirely subjective thing. What annoys me may not annoy you. An officious policeman may honestly believe that certain conduct say wearing a T-shirt saying, ''I kissed the Pope Down Under'' might be likely to annoy a pilgrim (and, probably, not that this is relevant, that the person wearing it intended it to be annoying). Another might simply think it amusing.

A magistrate hearing the charge might think it annoying, or she might not. We cannot have laws that depend on such subjective opinions. There must be some objective standard, so people know the law.

''Inconvenience'', however, can be an objective thing. As the court said, ''such inconvenience may arise, for example, where protesters by their locations or actions hinder or obstruct the movement of participants, or are so loud in their protest as to impair communications between groups of participants and officials''.

It, too, might be capable of being read too widely, and thus of conferring ''wide powers of uncertain ambit upon unauthorised persons''. But a court, interpreting and applying it, could more narrowly define it to limit it to matters of objective judgment. But ''annoyance'' was a word so wide that there was no intelligible boundary between what could validly be done by Parliament, and what could not.

Under attack were regulations made under a NSW Act of Parliament an Act not dissimilar from legislation passed during the Olympic Games and the Asia-Pacific Economic Cooperation protests. The regulations were challenged on constitutional grounds, as violating the so-called implied right of freedom of political communication.

Actually, the Federal Court made no ruling on whether this right was infringed. Instead its judgment was based on an old general principle that Parliament will not be taken to have interfered with long-established and generally agreed rights unless it has done so in the most explicit terms. Thus laws that could, read one way, interfere seriously with freedom of speech or movement will, if it is possible to find a more limited construction, be interpreted so as to make the least possible interference. The other essential principle behind the decision is judicial distaste for arbitrariness, uncertainty and subjectivity laws whose force depend on someone's opinion, rather than on verifiable and objective facts.

Three separate regulations were attacked but only one was struck out as vague and uncertain. Two others the one about inconveniencing others and another preventing the ''distribution'' of any but authorised materials at prescribed youth day venues were given narrow interpretations but not ruled entirely out of order. The challengers can take comfort from the fact that the court has made it clear that they are free to distribute pamphlets, condoms and other items. If police try to move them on because they are causing interference, it must be because they are restricting access or progress, or objectively interfering (perhaps with loud noises) with the exercise of the rights of others.

Courts have long had a distaste for making laws depend on police sensibilities, even as they recognised that police will sometimes need power and discretion to defuse dangerous situations, or to mediate the rights of different groups.

In the ACT 42 years ago, a young student, Des Ball, climbed up the King George V statue outside Parliament House during an anti-Vietnam protest, and hung a placard about the dear King's neck. When police arrested him, they charged him with ''offensive behaviour''. The case came before Justice John Kerr in the ACT Supreme Court.

Kerr said that behaviour, to be offensive, must be intended ''to wound the feelings, [or] arouse anger or resentment or outrage in the mind of a reasonable person''. It was an objective test, not what an individual policeman might feel personally.

''The average man, the reasonable man, being present on such an occasion, would see the defendant was engaged in a political demonstration. He would doubtless think that climbing on the pedestal and placing the placard on the statue was rather foolish and a misguided method of political protests, that it offended against the canons of good taste, that it was in that sense improper conduct.

''But I do not believe that the reasonable man, seeing such conduct to be truly political conduct, would have his feelings wounded, or anger, resentment, disgust or outrage roused ... I recognise that different minds may well come to different conclusions as to the reaction of the reasonable man in situations involving attitudes or beliefs and values in the community. But I believe that a so-called reasonable man is reasonably tolerant and understanding, and reasonably contemporary in his reactions.''

Or her reactions, assuming that one must now posit the existence of a reasonable woman as well.

The lesson is not that governments and administrators cannot stop demonstrations, or previously lawful exercises of rights, if they want and are prepared to take the political heat. If that is what Parliament wants, and it says so in unequivocal terms, it may well get it.

But the court recognises that citizens have a right to know with certainty what the law is. What the law is cannot depend on the subjective judgment of an official a judgment which might vary from person to person, or according to how she got out of bed in the morning. All the more so if the law has criminal or civil penalties, gives rights or creates obligations. One might not think that an unreasonable expectation, but it is amazing how many rights and freedoms, particularly ones buried in regulations, are matters of whim and discretion and the opinion not based on an objective test of some decision-maker.

Jack Waterford is Editor-at-Large.