My friend is in Slovenia and his visa expired 15 days ago. Does he have to pay some sort of penalty? What will happen to him and what should he do to travel back to his home country?
I'm not a lawyer, so take what is written below as purely informational.
The relevant law that deals with your friend's situation is referred to as the Foreigners Act (could only find the Slovenian language version). If you open that in Chrome and use its translate to English feature, you'll get a somewhat awkward translation of it. There is also a language selection dropdown at the top right of the page that pretty much does the same.
As per the Act, your friend is currently staying in the country illegally and may get fined 800 - 1200€ upon detection. Relevant articles seem to be 60 and 145 (crude translations below).
Article 60 (Illegal residence)
(1) It is considered that a foreigner is staying illegally in the Republic of Slovenia, if:
- he has illegally entered;
- does not have a visa or has an expired visa or if resides in the Republic of Slovenia contrary to the entry title or the time period, in which he was allowed to stay in Republic of Slovenia based on a law or an international agreement, has expired;
- does not have a residence permit or the permit has expired.
(1) A fine of 500 to 1,200€ shall be imposed on a foreigner for unauthorized entry into the Republic of Slovenia (Article 12 hereof).
(2) A fine of 800 to 1,200€ shall be imposed on a foreigner if:
- resides in the Republic of Slovenia contrary to the purpose for which he was granted a residence permit (fifth paragraph of Article 35 of this Law);
- staying illegally in the Republic of Slovenia (Article 60 of this Law).
I believe the proper course of action would be to visit a local police station and explain the situation. Your friend will probably be given a deadline by which he must leave Slovenia, according to Article 67 of the Act. He may be monitored during this time, either by being required to report to a police station daily or by staying in a residence designated by the police.
Slovenia was hit hard during the 2016 migration crisis and changed its legislation accordingly, so that blog entry (posted by @mkennedy) is no longer accurate as far as the fine goes.
Others have discussed specific penalties, but note that if you say nothing and just leave, it MIGHT not get noticed at the border. And if they do notice, the consequences might be easier than if they catch you when you are not trying to leave.
If I stay beyond 90 days (without a residence permit or a long term visa) or work in the Schengen area (without a working permit), what can happen?
A non-EU national who stays in the Schengen area beyond 90 days (without a residence permit or long-stay visa) is illegally present, which can result in a re-entry ban to the Schengen area. Working in the Schengen area without a work permit is also illegal (even if less than 90 days) and can likewise result in a re-entry ban to the Schengen area. Depending on the Member State administrative penalties may also apply.
Aliens shall be liable to a fine of between 400 and 1200 EUR for the following offences:
1) not possessing a valid travel document (Article 7); 2) not having a permit to enter the Republic of Slovenia (Article 8); 3) not leaving the country once their residence permit has expired
Aliens shall be liable to a fine of between 500 and 1200 EUR the following offences: 1) entering the Republic of Slovenia illegally (Article 11); 2) residing in the Republic of Slovenia in contravention of the purpose for which their residence permit was issued (fifth paragraph of Article 30); 3) residing in the Republic of Slovenia illegally (Article 47).