From the few countries I looked at, the general rules are:
- One can fly anywhere, as long as enforcing regulated and prohibited areas like other pilots.
- Regulated areas include inhabited areas, there is at least a minimum distance and often a minimum height.
- Pilots must plan their landing in authorized areas, taking elements into account. An emergency landing is still lawful, like for other types of flights. Many or most are due to pilot delaying the decision to terminate the flight.
- Pilot incapacitation may lead to emergency landing (by another person than the pilot), or to crash landing. Recently FAA was pushed by NTSB to act, at least on medical conditions required to fly.
- Pilots are supposed to be familiar with the related rules and NOTAMs.
- When it can be proved pilots have been careless or reckless, they are sanctioned.
I'm focusing on heated air balloons and excluding tethered, unmanned and high altitude balloons
A balloon pilot must plan their landing according to weather forecast, on a safe area, and only on a private property for which they have the authorization to land. When the intended flight cannot be followed because of a failure, because being short of gas, or because of atmospheric conditions, then an emergency landing must be carried on. As balloons have no control surface, that means the landing area cannot be selected, except by accelerating the descent or slowing it as long as possible (heating air or jettisoning ballast).
After the facts, in case of damage, if any person was injured or killed, if any complaint is issued or just if police is informed of the landing, then it's a matter of proving the pilot acted carelessly or recklessly.
If this is the case the pilot incurs civil and criminal penalties. E.g. pilot not acting in time in this event New Zealand:
K... v Civil Aviation Authority involved a fatal
incident. K... was convicted of breaching a former
civil aviation regulation by flying a balloon in
circumstances whereby avoidable danger to life or
property was likely to ensue. K... was piloting the
balloon when it was blown 200 metres offshore. The
balloon landed in the sea and three people
died. The trial judge found K... had failed to keep
proper lookout for weather changes during the
flight. K... was acquitted of one charge of
As for whether emergency landings are hazardous: They are, in particular the velocity and the vertical position of the gondola are not controlled. There are online accounts for serious injuries after uncontrolled landings and statistics from EASA (all EU countries, also includes collisions):
EASA statistics on balloon incidents and accidents, source
I was not able to determine exact rules for Netherlands, not even a summary of rules applicable to EU countries, however I'll give you the links to the legal framework for EU. But to start with, there are two approaches: Australia is rather liberal, no license is required, while US includes hot air balloons in general aviation aircraft.
Australia, regulated by CASA
In Australia commercial activities require a license but recreational ballooning is not regulated.
Balloon pilots can only land on private property if they, or their
support vehicle driver, have permission from the property owner.
Permission is not required in emergencies, or if no other landing site
Pilots must plan their flight based on forecast meteorological
conditions. However, changes in wind conditions could alter the
balloon's navigational tracking from that originally planned.
When over populated areas, balloons must fly at least 1000 feet above
ground level. When over other areas, balloons do not have to fly at a
US: Regulated by FAA
Perfectly lawful emergency landing in Illinois, source
Hot air balloon operations are conducted in accordance with FAR Part 91 (general aviation) and pilots must hold a license according to FAR Part 61, with a minimum of 10 hours of flight, 35 hours for a commercial pilot (more).
FAA issued a AC summarizing balloons operations.
Ballooning operations are regulated like other GA operations. In particular access to airspace of different classes follows the same constraints. Most flights occurs in class G airspace (uncontrolled) or E (controlled) and below 14,500 ft and all under VFR. FAR 91:119 still specifies minimum safe altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
The first paragraph requires the pilot to be able to execute an emergency landing at any time to prevent an accident.
Netherlands: Mostly regulated by EASA, with local details
As said, I was not able to find a summary of rules applicable to balloons in Netherlands, so you may need to read the highly indigestible documentation from EU, the main problem with the text is there are constant abstruse references to other texts, and seemingly no single composite version.
The base for aeronautical operations are the Standardised European Rules of the Air (SERA), complemented by the recent EC 2018/395. A license is required (EC 1178/2011). It includes a knowledge test in different domains, a medical certificate and 16 hours of flight, 50 for commercial flights (more).
Then there is a local act on aviation, The Wet Luchtvaart.
About flying areas, it seems the principle is similar to US, balloons are considered aircraft. Maybe specific to Netherlands, locations used by balloons for launch and landing are subject to authorization from the municipality.