This topic raises some interesting legal issues.
If the land is an aerodrome then the landowner is entitled to levy a charge for the use of the facility. It is custom and practice for aircraft/pilots to pay landing fees and therefore by using an aerodrome a pilot should expect to pay a fee for so doing. There may be some argument as to what level of fee could be expected and whether it is reasonable but equally it could be argued that as the pilot could foresee the requirement to pay a fee he should have ascertained what it was before visiting.
On the question of impounding an aircraft, an aerodrome owner could refuse an aircraft permission to taxi and take off and could take reasonable steps to prevent the commission of a crime.
Whilst some have opined that the answer would then be to remove the aircraft by road, that too could have some practical difficulties because Rule 41 provides:
41 (1) Unless there is a public right of way over it, a person or vehicle shall:
(a) not go onto any part of an aerodrome without the permission of the person in charge of that part of the aerodrome; and
(b) comply with any conditions subject to which that permission may be granted.
(2) A person or vehicle shall:
(a) not go onto or move on the manoeuvring area of an aerodrome which has an air traffic control unit or an aerodrome flight information service unit without the permission of that unit; and
(b) comply with any conditions subject to which that permission may be granted.
(3) Any permission granted for the purposes of this rule may be granted in respect of persons or vehicles generally, or in respect of any particular person or vehicle or any class of person or vehicle.
It would appear that if the land fits the definition of aerodrome the owner or person in charge could place severe restrictions on the recovery of the aircraft. The visiting pilot would then have to take legal action against the person for the return of the aircraft.
If landing in a field or disused airfield the landowner would not be entitled per se to a landing fee nor would you be committing an offence by removing the aircraft but the landowner would have a remedy in damages for trespass.