In Austria, the regulatory law is governed from the outset by two separate apects of police law:

• The state police law concerns public order.
• The security police law concerns public security.

Security Police law threatens "the causing of a justified disturbance" that "prejudices of public order" with penalty:

Prejudice of public order

Section 81.

(1) Anyone, who prejudices public order by a behaviour, that is likely to cause justified disturbance, commits an administrative offence and is to be punished by a fine of up to 500 EUR, unless the behaviour is justified, in particular by the use of a constitutionally guaranteed right. In the event of aggravating circumstances, instead of a fine, imprisonment can be imposed for up to one week, or up to two weeks for repeated offences.

(2) The bodies of the public security service must refrain of the arrest of a person, who was caught red-handed in the act of a disturbance of public order and who persists in spite of a warning in the continuation of the offence or seeks to repeat it (Section 35 Z 3 VStG), if the continuation or recurrence of the disturbance can be prevented by applying one or both of the less restrictive means (para. 3).

(3) As less restrictive means, the following means of direct forces of mandamus and compulsion are be considered:
1. the temporary ban of the disturber from the public place;
2. the confiscation of things, which are needed for the repetition of the disturbance.

(4) Confiscated objects are to be handed out on request
1. to whom, who was caught red-handed, as soon as the disturbance can not be repeated, or
2. to another person, who proves ownership or lawful possession of the objects, provided that there is a guarantee, that the disturbance will not be repeated with these objects.

(5) As long as the objects have not yet been handed over to the security authority, the person, who was caught red-handed, can send the request (para. 4) to the public security authority, who keep the objects.

(6) If a request (para. 4) is not filed within six months or if the claimant, demonstrably requested to do so, refrains (para. 4 no. 1 or 2) from picking the objects up from the authority, they shall be considered as forfeited. Incidentally, section 43 para. 2 is to be applied mutatis mutandis.

Source: “Bundesrecht konsolidiert: Gesamte Rechtsvorschrift für Sicherheitspolizeigesetz” (jusline.at)

The relevant terms of the Security Police law are

• Prejudice of public order and
• Causing a justified disturbance,

at which the relevant paragraph links both terms to each other, so they can not be considered individually.

Two examples:

Preservation of public decency

§ 11 Interdiction

(1) It is forbidden to violate public decency.

(2) Any violation of public decency is considered to be a gross violation of the generally accepted principles of decency observed in the public domain.

§ 12 Measures by the police

In order to terminate a violation of public decency, the authority may
a) temporarily ban persons, who commit a violation of public decency, from a public place;
b) confiscate objects.

§ 13 Sanction

Anyone, who violates public decency,, commits a regulatory offence and is to be punished by a fine of up to 360,- EUR.

Source: “Landesrecht konsolidiert Tirol: Gesamte Rechtsvorschrift für Landes-Polizeigesetz” (jusline.at)

Section 1 "Violation of decency and causing excessive noise", Security Law of the Federal State of Vienna [de: WLSG - Wiener Landes-Sicherheitsgesetz – WLSG], considered status of legislation: 1 August 2017

(1) Anyone, who
1. violates public decency or
2. improperly causes disturbing excessive noise or
3. summons a person in a public place to a deed or a sufferance with regard to her / his sexuality, although that person does not want it,
commits a regulatory offence and is to be punished with a fine of up to 700 EUR or, if not paid, with compensatory imprisonment up to one week.

(2) For the purpose of stopping or avoiding imminent continuation of mproper disturbing excessive noise, the bodies of the public security service may confiscate the objects, which are used to cause excessive noise, or, if this is not possible because of the nature of the objects or for other reasons, put them out of operation in a suitable manner.

(3) Confiscated objects are to be handed out on request
1. to whom, who was caught red-handed, as soon as the causing of excessive noise cannot be repeated, or
2. to another person, who proves ownership or lawful possession of the objects, provided that there is a guarantee, that the causing of excessive noise will not be repeated with these objects.

(4) As long as the objects have not yet been handed over to the security authority, the person, who was caught red-handed, can send the request (para. 3) to the public security authority, who keep the objects.

(5) If a request (para. 3) is not filed within six months or if the claimant, demonstrably requested to do so, refrains (para. 3 no. 1 or 2) from picking the objects up from the authority, they shall be considered as forfeited. In this case, the confiscated property must be commercialised or, if this is not possible or not permissible, destroyed. Any proceeds will be payable to the owner, if he so requests within three years after the expiry.

(6) Further or different national regulations concerning the causing of excessive noise remain unaffected.

Source: "Art. 1 § 1 WLSG Anstandsverletzung und Lärmerregung"" (jusline.at)

Section 3 "Defense against disturbances and assurance of public use", Security Law of the Federal State of Vienna, considered status of legislation: 1 August 2017

(1) Bodies of the public security service may instruct persons, to cease the following behavior or, if this is not appropriate, to leave the public place immediately:
If these persons
1. disturb other persons in public places in an unacceptable manner, in particular, when psychic stress is applied to persons approaching a social or medical institution, such as by insistent talking or (attempted) handover of objects, or
2. hinder other persons in public places to access public facilities, or
3. unacceptably impact on other persons in public places as to their intended use of public facilities.

(2) An unreasonable disturbance in terms of para. 1 no. 1 or unreasonable impairment within the meaning of para. 1 no. 3 is also present, if the behavior is likely, to cause reasonable disturbance for other persons through direct perception, and if it is either is not merely maintained for a short time only or if other persons are set in a state of intoxication, which apparently can no longer be controlled by the person responsible.

Source: “Art. 1 § 3 WLSG Abwehr von Belästigungen und Sicherung des Gemeingebrauchs” (jusline.at)

Here, relevant terms concerning order are:

1. “der ‘Öffentliche Anstand’, der verletzt wird durch ‘Verstoß gegen die allgemein anerkannten Grundsätze der Schicklichkeit in der Öffentlichkeit’”
   [en: “The ‘public decency’, which is violated by the ‘offence against the generally accepted principles of decency in public’”]
2. “ungebührlicher öffentlicher Lärm (zusammengefasst unter 5.)”
   [en: “unreasonable excessive noise in public (summarised in 5. "Unacceptable annoyance”)]
3. “Animierung zu Handlung oder Duldung von Handlungen der sexuelle Sphäre (zusammengefasst unter 5.)"
   [en: “encouraging or tolerating sexual actions (summarised in 5. "Unacceptable annoyance”)]
4. “unzumutbare Belästigung beim Zugang oder der Nutzung öffentlicher Einrichtungen (zusammengefasst unter 5.)"
   [en: “Unacceptable annoyance concerning access to or use of public facilities (summarised in 5. "Unacceptable annoyance”]
5. “unzumutbare Belästigung”
   [en: “unacceptable annoyance”]

With regard to nude hikes, no 1. is to be examined here in particular, especially since it refers to the "generally accepted principles of decency", which are surely subject to change over time also in Austria and therefore need to be questioned always promptly.

Relevant terms of Austrian police law as a whole are therefore:

• “Störung der öffentlichen Ordnung”
  [en: “Disturbance of public order”]
• “Erregung eines berechtigten Ärgernisses”
  [en: “legitimate disturbance"]
• “Verletzung des öffentlichen Anstandes”
  [en: “offence against public decency””]
• “Unzumutbare Belästigung” [en: “Unacceptable annoyance”]

It is noteworthy, however, that these terms are sometimes mentioned in pairs in the law, so that both must be fulfilled in order for the corresponding paragraph to be applicable:

§ 81 SPG: "Wer durch ein Verhalten, das geeignet ist, berechtigtes Ärgernis zu erregen, die öffentliche Ordnung stört, …" [en: “Anyone who disturbs public order by conduct, that is likely to cause legitimate disturbance, …"]

To examine the extent, to which nude hiking or similar activities can be associated with these terms, we consider, where available defining texts and some practical cases by Austrian justice.